Problem p03429 (C++)

Buggy submission (status: Runtime Error):
#define _CRT_SECURE_NO_WARNINGS
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, n) for (int i = 1; i <= (int)(n); i++)
#define all(V) V.begin(), V.end()
typedef long long lint;
typedef std::pair<lint, lint> P;
constexpr int INF = INT_MAX / 10;
constexpr lint LINF = LLONG_MAX / 2;
constexpr double eps = 1e-9;
template <class T>
class prique : public std::priority_queue<T, std::vector<T>, std::greater<T>> {
};

template <class T, class Alloc = std::allocator<T>> class Vector {

  using traits = std::allocator_traits<Alloc>;

public:
  using value_type = T;
  using allocator_type = Alloc;
  using size_type = unsigned int;
  using difference_type = int;
  using reference = T &;
  using const_reference = const T &;
  using pointer = typename traits::pointer;
  using const_pointer = typename traits::const_pointer;

  class iterator {

  public:
    using difference_type = int;
    using value_type = Vector::value_type;
    using pointer = Vector::pointer;
    using reference = Vector::reference;
    using iterator_category = std::random_access_iterator_tag;

  private:
    pointer p;

  public:
    iterator() noexcept : p() {}
    iterator(const Vector &base, difference_type index) noexcept
        : p(base.e + index) {}
    iterator(const iterator &i) : p(i.p) {}

    iterator &operator=(const iterator &i) = default;
    iterator &operator=(iterator &&i) noexcept = default;

    iterator &operator++() {
      p++;
      return *this;
    }

    iterator operator++(int) {
      iterator res = *this;
      p++;
      return res;
    }

    iterator operator+(const difference_type &x) const {
      iterator res = *this;
      return res += x;
    }

    iterator &operator+=(const difference_type &x) {
      p += x;
      return *this;
    }

    iterator &operator--() {
      p--;
      return *this;
    }

    iterator operator--(int) {
      iterator res = *this;
      p--;
      return res;
    }

    iterator operator-(const difference_type x) const {
      iterator res = *this;
      return res -= x;
    }

    difference_type operator-(const iterator &i) const { return p - i.p; }

    iterator &operator-=(const difference_type x) {
      p -= x;
      return *this;
    }

    reference operator*() const { return *p; }

    reference operator[](const difference_type x) const { return *(p + x); }

    bool operator<(const iterator &i) const { return p < i.p; }

    bool operator<=(const iterator &i) const { return p <= i.p; }

    bool operator==(const iterator &i) const { return p == i.p; }

    bool operator>(const iterator &i) const { return p > i.p; }

    bool operator>=(const iterator &i) const { return p >= i.p; }

    bool operator!=(const iterator &i) const { return p != i.p; }
  };

  class const_iterator {

  public:
    using difference_type = int;
    using value_type = Vector::value_type;
    using pointer = const Vector::pointer;
    using reference = const Vector::reference;
    using iterator_category = std::random_access_iterator_tag;

  private:
    pointer p;

  public:
    const_iterator() noexcept : p() {}
    const_iterator(const Vector &base, difference_type index) noexcept
        : p(base.e + index) {}
    const_iterator(const const_iterator &i) : p(i.p) {}

    const_iterator &operator=(const const_iterator &i) noexcept = default;
    const_iterator &operator=(const_iterator &&i) noexcept = default;

    const_iterator &operator++() {
      p++;
      return *this;
    }

    const_iterator operator++(int) {
      const_iterator res = *this;
      p++;
      return res;
    }

    const_iterator operator+(const difference_type x) const {
      const_iterator res = *this;
      return res += x;
    }

    const_iterator &operator+=(const difference_type x) {
      p += x;
      return *this;
    }

    const_iterator &operator--() {
      p--;
      return *this;
    }

    const_iterator operator--(int) {
      const_iterator res = *this;
      p--;
      return res;
    }

    const_iterator operator-(const difference_type x) const {
      const_iterator res = *this;
      return res -= x;
    }

    difference_type operator-(const const_iterator &i) const { return p - i.p; }

    const_iterator &operator-=(const difference_type x) {
      p -= x;
      return *this;
    }

    reference operator*() const { return *p; }

    reference operator[](const difference_type x) const { return *(p + x); }

    bool operator<(const const_iterator &i) const { return p < i.p; }

    bool operator<=(const const_iterator &i) const { return p <= i.p; }

    bool operator==(const const_iterator &i) const { return p == i.p; }

    bool operator>(const const_iterator &i) const { return p > i.p; }

    bool operator>=(const const_iterator &i) const { return p >= i.p; }

    bool operator!=(const const_iterator &i) const { return p != i.p; }
  };

  using reverse_iterator = std::reverse_iterator<iterator>;
  using const_reverse_iterator = std::reverse_iterator<const_iterator>;

private:
  pointer e;
  size_type length = 0, cap = 1;
  Alloc alloc;

  static_assert(
      std::is_same<T, typename Alloc::value_type>::value,
      "The allocator value type is not matched the Vector value type.");
  static_assert(!std::is_const<T>::value,
                "This library forbids containers of const elements");

public:
  Vector() : Vector(Alloc()) {}

  explicit Vector(const Alloc &a) noexcept : alloc(a) {
    e = alloc.allocate(cap);
  }

  explicit Vector(size_type n, const Alloc &a = Alloc()) : alloc(a) {
    while (cap < n)
      cap *= 2;
    e = alloc.allocate(cap);
    rep(i, n) emplace_back();
  }

  explicit Vector(size_type n, const_reference value, const Alloc &a = Alloc())
      : alloc(a) {
    while (cap < n)
      cap *= 2;
    e = alloc.allocate(cap);
    rep(i, n) emplace_back(value);
  }

  template <class InputIter>
  Vector(InputIter first, InputIter last, const Alloc &a = Alloc()) : alloc(a) {
    e = alloc.allocate(cap);
    for (InputIter i = first; i != last; i++) {
      emplace_back(*i);
    }
  }

  Vector(const Vector &x, const Alloc &a = Alloc()) : alloc(a) {
    while (cap < x.length)
      cap *= 2;
    length = x.length;
    e = alloc.allocate(cap);
    rep(i, x.length) traits::construct(alloc, e + i, *(x.e + i));
  }

  Vector(Vector &&x, const Alloc &a = Alloc()) : alloc(a) {
    cap = x.cap;
    length = x.length;
    e = x.e;
    x.e = nullptr;
  }

  ~Vector() {
    if (e != nullptr) {
      rep(i, length) traits::destroy(alloc, e + i);
      alloc.deallocate(e, cap);
    }
  }

  Vector &operator=(const Vector &x) {
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    length = x.length;
    cap = 1;
    while (cap < length)
      cap *= 2;
    e = alloc.allocate(cap);
    rep(i, length) traits::construct(alloc, e + i, *(x.e + i));
    return *this;
  }

  Vector &operator=(Vector &&x) {
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    cap = x.cap;
    length = x.length;
    e = x.e;
    x.e = nullptr;
    return *this;
  }

private:
  void extension() {
    pointer e_ = alloc.allocate(cap * 2);
    rep(i, length) traits::construct(alloc, e_ + i, *(e + i));
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    e = e_;
    cap *= 2;
  }

  void extension(size_type n) {
    unsigned int r = 1;
    while (cap * r < n)
      r *= 2;
    if (r == 1)
      return;
    pointer e_ = alloc.allocate(cap * r);
    rep(i, length) traits::construct(alloc, e_ + i, *(e + i));
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    e = e_;
    cap *= r;
  }

public:
  template <class InputIter> void assign(InputIter first, InputIter last) {
    size_type cnt = 0;
    for (InputIter i = first; i != last; i++) {
      if (cnt == cap) {
        length = std::max(length, cnt);
        extension();
      }
      traits::construct(alloc, e + cnt, *i);
      cnt++;
    }
  }

  void assign(size_type n, const_reference value) {
    extension(n);
    std::fill(e, e + n, value);
  }

  template <class... Args> void emplace_back(Args &&...args) {
    if (length == cap)
      extension();
    traits::construct(alloc, e + length, std::forward<Args>(args)...);
    length++;
  }

  void push_back(const_reference value) { emplace_back(value); }

  void push_back(T &&value) { emplace_back(std::move(value)); }

  void pop_back() {
    traits::destroy(alloc, e + length);
    length--;
  }

  void reserve(size_type n) { extension(n); }

  iterator erase(iterator pos) {
    const iterator res = pos;
    iterator t = pos;
    t++;
    for (iterator i = pos; t != end(); i++, t++) {
      *i = std::move(*t);
    }
    pop_back();
    return res;
  }

  iterator erase(iterator first, iterator last) {
    const iterator res = first;
    typename iterator::difference_type d = last - first;
    for (iterator i = first; i + d != end(); i++) {
      *i = std::move(*(i + d));
    }
    rep(i, d) pop_back();
    return res;
  }

  void swap(Vector &x) {
    std::swap(length, x.length);
    std::swap(cap, x.cap);
    std::swap(e, x.e);
  }

  void clear() {
    while (length)
      pop_back();
  }

  size_type size() const { return length; }

  void resize(size_type n, const_reference value = T()) {
    extension(n);
    while (n < length)
      pop_back();
    length = n;
    std::fill(e, e + n, value);
  }

  size_type capacity() const { return cap; }

  bool empty() const { return !length; }

  reference operator[](const size_type pos) const { return e[pos]; }

  pointer data() { return e; }

  reference front() { return *e; }

  reference back() { return *(e + length - 1); }

  iterator begin() noexcept { return iterator(*this, 0); }

  const_iterator begin() const noexcept { return const_iterator(*this, 0); }

  const_iterator cbegin() const noexcept { return const_iterator(*this, 0); }

  iterator rbegin() noexcept { return reverse_iterator(*this, 0); }

  const_iterator rbegin() const noexcept {
    return const_reverse_iterator(*this, 0);
  }

  const_iterator crbegin() const noexcept {
    return const_reverse_iterator(*this, 0);
  }

  iterator end() noexcept { return iterator(*this, length); }

  const_iterator end() const noexcept { return const_iterator(*this, length); }

  const_iterator cend() const noexcept { return const_iterator(*this, length); }

  iterator rend() noexcept { return reverse_iterator(*this, length); }

  const_iterator rend() const noexcept {
    return const_reverse_iterator(*this, length);
  }

  const_iterator crend() const noexcept {
    return const_reverse_iterator(*this, length);
  }
};
template <class T, class U> inline bool chmax(T &lhs, const U &rhs) {
  if (lhs < rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
template <class T, class U> inline bool chmin(T &lhs, const U &rhs) {
  if (lhs > rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
inline lint gcd(lint a, lint b) {
  while (b) {
    lint c = a;
    a = b;
    b = c % b;
  }
  return a;
}
inline lint lcm(lint a, lint b) { return a / gcd(a, b) * b; }
bool isprime(lint n) {
  if (n == 1)
    return false;
  for (int i = 2; i * i <= n; i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}
lint mypow(lint a, lint b) {
  if (!b)
    return 1;
  if (b & 1)
    return mypow(a, b - 1) * a;
  lint memo = mypow(a, b >> 1);
  return memo * memo;
}
lint modpow(lint a, lint b, lint m) {
  if (!b)
    return 1;
  if (b & 1)
    return modpow(a, b - 1, m) * a % m;
  lint memo = modpow(a, b >> 1, m);
  return memo * memo % m;
}
template <typename T> void printArray(std::vector<T> &vec) {
  rep(i, vec.size() - 1) std::cout << vec[i] << " ";
  std::cout << vec.back() << std::endl;
}
template <typename T> void printArray(Vector<T> &vec) {
  rep(i, vec.size() - 1) std::cout << vec[i] << " ";
  std::cout << vec.back() << std::endl;
}
template <typename T> void printArray(T l, T r) {
  T rprev = r;
  rprev--;
  for (T i = l; i != rprev; i++) {
    std::cout << *i << " ";
  }
  std::cout << *rprev << std::endl;
}
std::string to_string(Vector<int> &vec) {
  std::string res = "[";
  rep(i, vec.size() - 1) res += std::to_string(vec[i]) + ", ";
  res += std::to_string(vec.back()) + "]";
  return res;
}
template <unsigned int modulo = 1000000007> class ModInt {
  lint value;

public:
  ModInt() : value(0) {}
  template <typename T> ModInt(T value = 0) : value(value) {
    if (value < 0)
      value = -(lint)(-value % modulo) + modulo;
    this->value = value % modulo;
  }
  inline operator int() const { return value; }
  inline ModInt &operator+=(const ModInt &x) {
    value += x.value;
    if (value >= modulo)
      value -= modulo;
    return *this;
  }
  inline ModInt &operator++() {
    if (value == modulo - 1)
      value = 0;
    else
      value++;
    return *this;
  }
  inline ModInt operator-() const { return ModInt(0) -= *this; }
  inline ModInt &operator-=(const ModInt &x) {
    value -= x.value;
    if (value < 0)
      value += modulo;
    return *this;
  }
  inline ModInt &operator--() {
    if (value == 0)
      value = modulo - 1;
    else
      value--;
    return *this;
  }
  inline ModInt &operator*=(const ModInt &x) {
    value = value * x.value % modulo;
    return *this;
  }
  inline ModInt &operator/=(ModInt rhs) {
    int exp = modulo - 2;
    while (exp) {
      if (exp & 1)
        *this *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return *this;
  }
  template <typename T> ModInt operator+(const T &rhs) const {
    return ModInt(*this) += rhs;
  }
  template <typename T> ModInt &operator+=(const T &rhs) {
    return operator+=(ModInt(rhs));
  }
  template <typename T> ModInt operator-(const T &rhs) const {
    return ModInt(*this) -= rhs;
  }
  template <typename T> ModInt &operator-=(const T &rhs) {
    return operator-=(ModInt(rhs));
  }
  template <typename T> ModInt operator*(const T &rhs) const {
    return ModInt(*this) *= rhs;
  }
  template <typename T> ModInt &operator*=(const T &rhs) {
    return operator*=(ModInt(rhs));
  }
  template <typename T> ModInt operator/(const T &rhs) const {
    return ModInt(*this) /= rhs;
  }
  template <typename T> ModInt &operator/=(const T &rhs) {
    return operator/=(ModInt(rhs));
  }
};
template <unsigned int T>
std::istream &operator>>(std::istream &ist, ModInt<T> &x) {
  lint a;
  ist >> a;
  x = a;
  return ist;
}
int n, m, a, b;
char ans[1010][1010];
int main() {
  std::cin >> n >> m >> a >> b;
  rep(i, n) { rep(j, m) ans[i][j] = 'x'; }
  if ((a + b) * 2 > n * m) {
    puts("NO");
    return 0;
  }
  if (n % 2 == 0 && m % 2 == 0) {
    if (a % 2 && b % 2 && (a + b) * 2 == n * m) {
      puts("NO");
      return 0;
    }
    rep(i, n) {
      for (int j = 0; j < m; j += 2) {
        ans[i][j] = '<';
        ans[i][j + 1] = '>';
      }
    }
    int cnt = 0;
    for (int i = 0; i < n; i += 2) {
      bool f = false;
      for (int j = 0; j < m; j += 2) {
        if (b <= cnt) {
          f = true;
          break;
        }
        ans[i][j] = ans[i][j + 1] = '^';
        ans[i + 1][j] = ans[i + 1][j + 1] = 'v';
        cnt += 2;
        if (b < cnt) {
          ans[i][j + 1] = ans[i + 1][j + 1] = '.';
        }
      }
      if (f)
        break;
    }
    cnt = n * m / 2 - (b + 1) / 2 * 2;
    rep(i, n) {
      bool f = false;
      for (int j = 0; j < m; j += 2) {
        if (a == cnt) {
          f = true;
          break;
        }
        if (ans[i][j] == '<') {
          ans[i][j] = ans[i][j + 1] = '.';
          cnt--;
        }
      }
      if (f)
        break;
    }
    puts("YES");
    rep(i, n) {
      rep(j, m) std::cout << ans[i][j];
      std::cout << std::endl;
    }
  } else if (n % 2 && m % 2 == 0) {
    if (a < m / 2) {
      if ((a + b) * 2 > n * m - (m - 2 * a)) {
        puts("NO");
        return 0;
      }
      rep(i, a) {
        ans[0][2 * i] = '<';
        ans[0][2 * i + 1] = '>';
      }
    } else {
      if ((a - (m / 2)) % 2 && (a + b) * 2 >= n * m) {
        puts("NO");
        return 0;
      }
      for (int i = 0; i < m; i += 2) {
        ans[0][i] = '<';
        ans[0][i + 1] = '>';
        a--;
      }
      for (int i = 1; i < n; i += 2) {
        bool f = false;
        for (int j = 0; j < m; j += 2) {
          if (a == 0) {
            f = true;
            break;
          }
          ans[i][j] = ans[i + 1][j] = '<';
          ans[i][j + 1] = ans[i + 1][j + 1] = '>';
          a -= 2;
          if (a == -1) {
            ans[i + 1][j] = ans[i + 1][j + 1] = 'x';
            f = true;
            break;
          }
        }
        if (f)
          break;
      }
    }
    int cnt = 0;
    rep(i, n - 1) {
      bool f = false;
      rep(j, m) {
        if (cnt == b) {
          f = true;
          break;
        }
        if (ans[i][j] == 'x' && ans[i + 1][j] == 'x') {
          ans[i][j] = '^';
          ans[i + 1][j] = 'v';
          cnt++;
        }
      }
      if (f)
        break;
    }
    rep(i, n) {
      rep(j, m) {
        if (ans[i][j] == 'x')
          ans[i][j] = '.';
      }
    }
    puts("YES");
    rep(i, n) {
      rep(j, m) std::cout << ans[i][j];
      std::cout << std::endl;
    }
  } else if (n % 2 == 0 && m % 2) {
    if (b < n / 2) {
      if ((a + b) * 2 > n * m - (n - 2 * b)) {
        puts("NO");
        return 0;
      }
      rep(i, b) {
        ans[2 * i][0] = '^';
        ans[2 * i + 1][0] = 'v';
      }
    } else {
      if ((b - n / 2) % 2 && (a + b) * 2 >= n * m) {
        puts("NO");
        return 0;
      }
      for (int i = 0; i < n; i += 2) {
        ans[i][0] = '^';
        ans[i + 1][0] = 'v';
        b--;
      }
      for (int i = 1; i < m; i += 2) {
        bool f = false;
        for (int j = 0; j < n; j += 2) {
          if (b == 0) {
            f = true;
            break;
          }
          ans[j][i] = ans[j][i + 1] = '^';
          ans[j + 1][i] = ans[j + 1][i + 1] = 'v';
          b -= 2;
          if (b == -1) {
            ans[j][i + 1] = ans[j + 1][i + 1] = 'x';
            f = true;
            break;
          }
        }
        if (f)
          break;
      }
    }
    int cnt = 0;
    rep(i, n) {
      bool f = false;
      rep(j, m - 1) {
        if (cnt == a) {
          f = true;
          break;
        }
        if (ans[i][j] == 'x' && ans[i][j + 1] == 'x') {
          ans[i][j] = '<';
          ans[i][j + 1] = '>';
          cnt++;
        }
      }
      if (f)
        break;
    }
    rep(i, n) {
      rep(j, m) {
        if (ans[i][j] == 'x')
          ans[i][j] = '.';
      }
    }
    puts("YES");
    rep(i, n) {
      rep(j, m) std::cout << ans[i][j];
      std::cout << std::endl;
    }
  } else
    return 1;
  return 0;
}

Fixed submission:
#define _CRT_SECURE_NO_WARNINGS
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, n) for (int i = 1; i <= (int)(n); i++)
#define all(V) V.begin(), V.end()
typedef long long lint;
typedef std::pair<lint, lint> P;
constexpr int INF = INT_MAX / 10;
constexpr lint LINF = LLONG_MAX / 2;
constexpr double eps = 1e-9;
template <class T>
class prique : public std::priority_queue<T, std::vector<T>, std::greater<T>> {
};

template <class T, class Alloc = std::allocator<T>> class Vector {

  using traits = std::allocator_traits<Alloc>;

public:
  using value_type = T;
  using allocator_type = Alloc;
  using size_type = unsigned int;
  using difference_type = int;
  using reference = T &;
  using const_reference = const T &;
  using pointer = typename traits::pointer;
  using const_pointer = typename traits::const_pointer;

  class iterator {

  public:
    using difference_type = int;
    using value_type = Vector::value_type;
    using pointer = Vector::pointer;
    using reference = Vector::reference;
    using iterator_category = std::random_access_iterator_tag;

  private:
    pointer p;

  public:
    iterator() noexcept : p() {}
    iterator(const Vector &base, difference_type index) noexcept
        : p(base.e + index) {}
    iterator(const iterator &i) : p(i.p) {}

    iterator &operator=(const iterator &i) = default;
    iterator &operator=(iterator &&i) noexcept = default;

    iterator &operator++() {
      p++;
      return *this;
    }

    iterator operator++(int) {
      iterator res = *this;
      p++;
      return res;
    }

    iterator operator+(const difference_type &x) const {
      iterator res = *this;
      return res += x;
    }

    iterator &operator+=(const difference_type &x) {
      p += x;
      return *this;
    }

    iterator &operator--() {
      p--;
      return *this;
    }

    iterator operator--(int) {
      iterator res = *this;
      p--;
      return res;
    }

    iterator operator-(const difference_type x) const {
      iterator res = *this;
      return res -= x;
    }

    difference_type operator-(const iterator &i) const { return p - i.p; }

    iterator &operator-=(const difference_type x) {
      p -= x;
      return *this;
    }

    reference operator*() const { return *p; }

    reference operator[](const difference_type x) const { return *(p + x); }

    bool operator<(const iterator &i) const { return p < i.p; }

    bool operator<=(const iterator &i) const { return p <= i.p; }

    bool operator==(const iterator &i) const { return p == i.p; }

    bool operator>(const iterator &i) const { return p > i.p; }

    bool operator>=(const iterator &i) const { return p >= i.p; }

    bool operator!=(const iterator &i) const { return p != i.p; }
  };

  class const_iterator {

  public:
    using difference_type = int;
    using value_type = Vector::value_type;
    using pointer = const Vector::pointer;
    using reference = const Vector::reference;
    using iterator_category = std::random_access_iterator_tag;

  private:
    pointer p;

  public:
    const_iterator() noexcept : p() {}
    const_iterator(const Vector &base, difference_type index) noexcept
        : p(base.e + index) {}
    const_iterator(const const_iterator &i) : p(i.p) {}

    const_iterator &operator=(const const_iterator &i) noexcept = default;
    const_iterator &operator=(const_iterator &&i) noexcept = default;

    const_iterator &operator++() {
      p++;
      return *this;
    }

    const_iterator operator++(int) {
      const_iterator res = *this;
      p++;
      return res;
    }

    const_iterator operator+(const difference_type x) const {
      const_iterator res = *this;
      return res += x;
    }

    const_iterator &operator+=(const difference_type x) {
      p += x;
      return *this;
    }

    const_iterator &operator--() {
      p--;
      return *this;
    }

    const_iterator operator--(int) {
      const_iterator res = *this;
      p--;
      return res;
    }

    const_iterator operator-(const difference_type x) const {
      const_iterator res = *this;
      return res -= x;
    }

    difference_type operator-(const const_iterator &i) const { return p - i.p; }

    const_iterator &operator-=(const difference_type x) {
      p -= x;
      return *this;
    }

    reference operator*() const { return *p; }

    reference operator[](const difference_type x) const { return *(p + x); }

    bool operator<(const const_iterator &i) const { return p < i.p; }

    bool operator<=(const const_iterator &i) const { return p <= i.p; }

    bool operator==(const const_iterator &i) const { return p == i.p; }

    bool operator>(const const_iterator &i) const { return p > i.p; }

    bool operator>=(const const_iterator &i) const { return p >= i.p; }

    bool operator!=(const const_iterator &i) const { return p != i.p; }
  };

  using reverse_iterator = std::reverse_iterator<iterator>;
  using const_reverse_iterator = std::reverse_iterator<const_iterator>;

private:
  pointer e;
  size_type length = 0, cap = 1;
  Alloc alloc;

  static_assert(
      std::is_same<T, typename Alloc::value_type>::value,
      "The allocator value type is not matched the Vector value type.");
  static_assert(!std::is_const<T>::value,
                "This library forbids containers of const elements");

public:
  Vector() : Vector(Alloc()) {}

  explicit Vector(const Alloc &a) noexcept : alloc(a) {
    e = alloc.allocate(cap);
  }

  explicit Vector(size_type n, const Alloc &a = Alloc()) : alloc(a) {
    while (cap < n)
      cap *= 2;
    e = alloc.allocate(cap);
    rep(i, n) emplace_back();
  }

  explicit Vector(size_type n, const_reference value, const Alloc &a = Alloc())
      : alloc(a) {
    while (cap < n)
      cap *= 2;
    e = alloc.allocate(cap);
    rep(i, n) emplace_back(value);
  }

  template <class InputIter>
  Vector(InputIter first, InputIter last, const Alloc &a = Alloc()) : alloc(a) {
    e = alloc.allocate(cap);
    for (InputIter i = first; i != last; i++) {
      emplace_back(*i);
    }
  }

  Vector(const Vector &x, const Alloc &a = Alloc()) : alloc(a) {
    while (cap < x.length)
      cap *= 2;
    length = x.length;
    e = alloc.allocate(cap);
    rep(i, x.length) traits::construct(alloc, e + i, *(x.e + i));
  }

  Vector(Vector &&x, const Alloc &a = Alloc()) : alloc(a) {
    cap = x.cap;
    length = x.length;
    e = x.e;
    x.e = nullptr;
  }

  ~Vector() {
    if (e != nullptr) {
      rep(i, length) traits::destroy(alloc, e + i);
      alloc.deallocate(e, cap);
    }
  }

  Vector &operator=(const Vector &x) {
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    length = x.length;
    cap = 1;
    while (cap < length)
      cap *= 2;
    e = alloc.allocate(cap);
    rep(i, length) traits::construct(alloc, e + i, *(x.e + i));
    return *this;
  }

  Vector &operator=(Vector &&x) {
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    cap = x.cap;
    length = x.length;
    e = x.e;
    x.e = nullptr;
    return *this;
  }

private:
  void extension() {
    pointer e_ = alloc.allocate(cap * 2);
    rep(i, length) traits::construct(alloc, e_ + i, *(e + i));
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    e = e_;
    cap *= 2;
  }

  void extension(size_type n) {
    unsigned int r = 1;
    while (cap * r < n)
      r *= 2;
    if (r == 1)
      return;
    pointer e_ = alloc.allocate(cap * r);
    rep(i, length) traits::construct(alloc, e_ + i, *(e + i));
    rep(i, length) traits::destroy(alloc, e + i);
    alloc.deallocate(e, cap);
    e = e_;
    cap *= r;
  }

public:
  template <class InputIter> void assign(InputIter first, InputIter last) {
    size_type cnt = 0;
    for (InputIter i = first; i != last; i++) {
      if (cnt == cap) {
        length = std::max(length, cnt);
        extension();
      }
      traits::construct(alloc, e + cnt, *i);
      cnt++;
    }
  }

  void assign(size_type n, const_reference value) {
    extension(n);
    std::fill(e, e + n, value);
  }

  template <class... Args> void emplace_back(Args &&...args) {
    if (length == cap)
      extension();
    traits::construct(alloc, e + length, std::forward<Args>(args)...);
    length++;
  }

  void push_back(const_reference value) { emplace_back(value); }

  void push_back(T &&value) { emplace_back(std::move(value)); }

  void pop_back() {
    traits::destroy(alloc, e + length);
    length--;
  }

  void reserve(size_type n) { extension(n); }

  iterator erase(iterator pos) {
    const iterator res = pos;
    iterator t = pos;
    t++;
    for (iterator i = pos; t != end(); i++, t++) {
      *i = std::move(*t);
    }
    pop_back();
    return res;
  }

  iterator erase(iterator first, iterator last) {
    const iterator res = first;
    typename iterator::difference_type d = last - first;
    for (iterator i = first; i + d != end(); i++) {
      *i = std::move(*(i + d));
    }
    rep(i, d) pop_back();
    return res;
  }

  void swap(Vector &x) {
    std::swap(length, x.length);
    std::swap(cap, x.cap);
    std::swap(e, x.e);
  }

  void clear() {
    while (length)
      pop_back();
  }

  size_type size() const { return length; }

  void resize(size_type n, const_reference value = T()) {
    extension(n);
    while (n < length)
      pop_back();
    length = n;
    std::fill(e, e + n, value);
  }

  size_type capacity() const { return cap; }

  bool empty() const { return !length; }

  reference operator[](const size_type pos) const { return e[pos]; }

  pointer data() { return e; }

  reference front() { return *e; }

  reference back() { return *(e + length - 1); }

  iterator begin() noexcept { return iterator(*this, 0); }

  const_iterator begin() const noexcept { return const_iterator(*this, 0); }

  const_iterator cbegin() const noexcept { return const_iterator(*this, 0); }

  iterator rbegin() noexcept { return reverse_iterator(*this, 0); }

  const_iterator rbegin() const noexcept {
    return const_reverse_iterator(*this, 0);
  }

  const_iterator crbegin() const noexcept {
    return const_reverse_iterator(*this, 0);
  }

  iterator end() noexcept { return iterator(*this, length); }

  const_iterator end() const noexcept { return const_iterator(*this, length); }

  const_iterator cend() const noexcept { return const_iterator(*this, length); }

  iterator rend() noexcept { return reverse_iterator(*this, length); }

  const_iterator rend() const noexcept {
    return const_reverse_iterator(*this, length);
  }

  const_iterator crend() const noexcept {
    return const_reverse_iterator(*this, length);
  }
};
template <class T, class U> inline bool chmax(T &lhs, const U &rhs) {
  if (lhs < rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
template <class T, class U> inline bool chmin(T &lhs, const U &rhs) {
  if (lhs > rhs) {
    lhs = rhs;
    return 1;
  }
  return 0;
}
inline lint gcd(lint a, lint b) {
  while (b) {
    lint c = a;
    a = b;
    b = c % b;
  }
  return a;
}
inline lint lcm(lint a, lint b) { return a / gcd(a, b) * b; }
bool isprime(lint n) {
  if (n == 1)
    return false;
  for (int i = 2; i * i <= n; i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}
lint mypow(lint a, lint b) {
  if (!b)
    return 1;
  if (b & 1)
    return mypow(a, b - 1) * a;
  lint memo = mypow(a, b >> 1);
  return memo * memo;
}
lint modpow(lint a, lint b, lint m) {
  if (!b)
    return 1;
  if (b & 1)
    return modpow(a, b - 1, m) * a % m;
  lint memo = modpow(a, b >> 1, m);
  return memo * memo % m;
}
template <typename T> void printArray(std::vector<T> &vec) {
  rep(i, vec.size() - 1) std::cout << vec[i] << " ";
  std::cout << vec.back() << std::endl;
}
template <typename T> void printArray(Vector<T> &vec) {
  rep(i, vec.size() - 1) std::cout << vec[i] << " ";
  std::cout << vec.back() << std::endl;
}
template <typename T> void printArray(T l, T r) {
  T rprev = r;
  rprev--;
  for (T i = l; i != rprev; i++) {
    std::cout << *i << " ";
  }
  std::cout << *rprev << std::endl;
}
std::string to_string(Vector<int> &vec) {
  std::string res = "[";
  rep(i, vec.size() - 1) res += std::to_string(vec[i]) + ", ";
  res += std::to_string(vec.back()) + "]";
  return res;
}
template <unsigned int modulo = 1000000007> class ModInt {
  lint value;

public:
  ModInt() : value(0) {}
  template <typename T> ModInt(T value = 0) : value(value) {
    if (value < 0)
      value = -(lint)(-value % modulo) + modulo;
    this->value = value % modulo;
  }
  inline operator int() const { return value; }
  inline ModInt &operator+=(const ModInt &x) {
    value += x.value;
    if (value >= modulo)
      value -= modulo;
    return *this;
  }
  inline ModInt &operator++() {
    if (value == modulo - 1)
      value = 0;
    else
      value++;
    return *this;
  }
  inline ModInt operator-() const { return ModInt(0) -= *this; }
  inline ModInt &operator-=(const ModInt &x) {
    value -= x.value;
    if (value < 0)
      value += modulo;
    return *this;
  }
  inline ModInt &operator--() {
    if (value == 0)
      value = modulo - 1;
    else
      value--;
    return *this;
  }
  inline ModInt &operator*=(const ModInt &x) {
    value = value * x.value % modulo;
    return *this;
  }
  inline ModInt &operator/=(ModInt rhs) {
    int exp = modulo - 2;
    while (exp) {
      if (exp & 1)
        *this *= rhs;
      rhs *= rhs;
      exp >>= 1;
    }
    return *this;
  }
  template <typename T> ModInt operator+(const T &rhs) const {
    return ModInt(*this) += rhs;
  }
  template <typename T> ModInt &operator+=(const T &rhs) {
    return operator+=(ModInt(rhs));
  }
  template <typename T> ModInt operator-(const T &rhs) const {
    return ModInt(*this) -= rhs;
  }
  template <typename T> ModInt &operator-=(const T &rhs) {
    return operator-=(ModInt(rhs));
  }
  template <typename T> ModInt operator*(const T &rhs) const {
    return ModInt(*this) *= rhs;
  }
  template <typename T> ModInt &operator*=(const T &rhs) {
    return operator*=(ModInt(rhs));
  }
  template <typename T> ModInt operator/(const T &rhs) const {
    return ModInt(*this) /= rhs;
  }
  template <typename T> ModInt &operator/=(const T &rhs) {
    return operator/=(ModInt(rhs));
  }
};
template <unsigned int T>
std::istream &operator>>(std::istream &ist, ModInt<T> &x) {
  lint a;
  ist >> a;
  x = a;
  return ist;
}
int n, m, a, b;
char ans[1010][1010];
int main() {
  std::cin >> n >> m >> a >> b;
  rep(i, n) { rep(j, m) ans[i][j] = 'x'; }
  if ((a + b) * 2 > n * m) {
    puts("NO");
    return 0;
  }
  if (n % 2 == 0 && m % 2 == 0) {
    if (a % 2 && b % 2 && (a + b) * 2 == n * m) {
      puts("NO");
      return 0;
    }
    rep(i, n) {
      for (int j = 0; j < m; j += 2) {
        ans[i][j] = '<';
        ans[i][j + 1] = '>';
      }
    }
    int cnt = 0;
    for (int i = 0; i < n; i += 2) {
      bool f = false;
      for (int j = 0; j < m; j += 2) {
        if (b <= cnt) {
          f = true;
          break;
        }
        ans[i][j] = ans[i][j + 1] = '^';
        ans[i + 1][j] = ans[i + 1][j + 1] = 'v';
        cnt += 2;
        if (b < cnt) {
          ans[i][j + 1] = ans[i + 1][j + 1] = '.';
        }
      }
      if (f)
        break;
    }
    cnt = n * m / 2 - (b + 1) / 2 * 2;
    rep(i, n) {
      bool f = false;
      for (int j = 0; j < m; j += 2) {
        if (a == cnt) {
          f = true;
          break;
        }
        if (ans[i][j] == '<') {
          ans[i][j] = ans[i][j + 1] = '.';
          cnt--;
        }
      }
      if (f)
        break;
    }
    puts("YES");
    rep(i, n) {
      rep(j, m) std::cout << ans[i][j];
      std::cout << std::endl;
    }
  } else if (n % 2 && m % 2 == 0) {
    if (a < m / 2) {
      if ((a + b) * 2 > n * m - (m - 2 * a)) {
        puts("NO");
        return 0;
      }
      rep(i, a) {
        ans[0][2 * i] = '<';
        ans[0][2 * i + 1] = '>';
      }
    } else {
      if ((a - (m / 2)) % 2 && (a + b) * 2 >= n * m) {
        puts("NO");
        return 0;
      }
      for (int i = 0; i < m; i += 2) {
        ans[0][i] = '<';
        ans[0][i + 1] = '>';
        a--;
      }
      for (int i = 1; i < n; i += 2) {
        bool f = false;
        for (int j = 0; j < m; j += 2) {
          if (a == 0) {
            f = true;
            break;
          }
          ans[i][j] = ans[i + 1][j] = '<';
          ans[i][j + 1] = ans[i + 1][j + 1] = '>';
          a -= 2;
          if (a == -1) {
            ans[i + 1][j] = ans[i + 1][j + 1] = 'x';
            f = true;
            break;
          }
        }
        if (f)
          break;
      }
    }
    int cnt = 0;
    rep(i, n - 1) {
      bool f = false;
      rep(j, m) {
        if (cnt == b) {
          f = true;
          break;
        }
        if (ans[i][j] == 'x' && ans[i + 1][j] == 'x') {
          ans[i][j] = '^';
          ans[i + 1][j] = 'v';
          cnt++;
        }
      }
      if (f)
        break;
    }
    rep(i, n) {
      rep(j, m) {
        if (ans[i][j] == 'x')
          ans[i][j] = '.';
      }
    }
    puts("YES");
    rep(i, n) {
      rep(j, m) std::cout << ans[i][j];
      std::cout << std::endl;
    }
  } else if (n % 2 == 0 && m % 2) {
    if (b < n / 2) {
      if ((a + b) * 2 > n * m - (n - 2 * b)) {
        puts("NO");
        return 0;
      }
      rep(i, b) {
        ans[2 * i][0] = '^';
        ans[2 * i + 1][0] = 'v';
      }
    } else {
      if ((b - n / 2) % 2 && (a + b) * 2 >= n * m) {
        puts("NO");
        return 0;
      }
      for (int i = 0; i < n; i += 2) {
        ans[i][0] = '^';
        ans[i + 1][0] = 'v';
        b--;
      }
      for (int i = 1; i < m; i += 2) {
        bool f = false;
        for (int j = 0; j < n; j += 2) {
          if (b == 0) {
            f = true;
            break;
          }
          ans[j][i] = ans[j][i + 1] = '^';
          ans[j + 1][i] = ans[j + 1][i + 1] = 'v';
          b -= 2;
          if (b == -1) {
            ans[j][i + 1] = ans[j + 1][i + 1] = 'x';
            f = true;
            break;
          }
        }
        if (f)
          break;
      }
    }
    int cnt = 0;
    rep(i, n) {
      bool f = false;
      rep(j, m - 1) {
        if (cnt == a) {
          f = true;
          break;
        }
        if (ans[i][j] == 'x' && ans[i][j + 1] == 'x') {
          ans[i][j] = '<';
          ans[i][j + 1] = '>';
          cnt++;
        }
      }
      if (f)
        break;
    }
    rep(i, n) {
      rep(j, m) {
        if (ans[i][j] == 'x')
          ans[i][j] = '.';
      }
    }
    puts("YES");
    rep(i, n) {
      rep(j, m) std::cout << ans[i][j];
      std::cout << std::endl;
    }
  } else {
    if (a < m / 2) {
      if ((a + b) * 2 > n * m - (m - 2 * a)) {
        puts("NO");
        return 0;
      }
      rep(i, a) {
        ans[0][2 * i] = '<';
        ans[0][2 * i + 1] = '>';
      }
    } else {
      if (a * 2 > n * m - n || (a + b) * 2 > n * m - 1) {
        puts("NO");
        return 0;
      }
      for (int i = 0; i < m - 1; i += 2) {
        ans[0][i] = '<';
        ans[0][i + 1] = '>';
        a--;
      }
      if (a % 2) {
        ans[n - 1][m - 2] = '<';
        ans[n - 1][m - 1] = '>';
        a--;
      }
      for (int i = 1; i < n; i += 2) {
        bool f = false;
        for (int j = 0; j < m - 1; j += 2) {
          if (a == 0) {
            f = true;
            break;
          }
          ans[i][j] = ans[i + 1][j] = '<';
          ans[i][j + 1] = ans[i + 1][j + 1] = '>';
          a -= 2;
          if (a == -1) {
            ans[i + 1][j] = ans[i + 1][j + 1] = 'x';
            f = true;
            break;
          }
        }
        if (f)
          break;
      }
    }
    int cnt = 0;
    rep(i, n - 1) {
      bool f = false;
      rep(j, m) {
        if (cnt == b) {
          f = true;
          break;
        }
        if (ans[i][j] == 'x' && ans[i + 1][j] == 'x') {
          ans[i][j] = '^';
          ans[i + 1][j] = 'v';
          cnt++;
        }
      }
      if (f)
        break;
    }
    rep(i, n) {
      rep(j, m) {
        if (ans[i][j] == 'x')
          ans[i][j] = '.';
      }
    }
    puts("YES");
    rep(i, n) {
      rep(j, m) std::cout << ans[i][j];
      std::cout << std::endl;
    }
  }
  return 0;
}