Problem p03660 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

#define f(i, n) for (int i = 0; i < (n); i++)

#define inf (int)(3e18)
#define int long long
#define mod (int)(1000000007)

#define intt long long

using namespace std;

// Library
// モッドパウ
int modpow(int x, int y, int m = mod) {
  int res = 1;
  while (y) {
    if (y % 2) {
      res *= x;
      res %= m;
    }
    x = x * x % mod;
    y /= 2;
  }
  return res;
}

int mypow(int x, int y) {
  int res = 1;
  while (y) {
    if (y % 2) {
      res *= x;
    }
    x = x * x;
    y /= 2;
  }
  return res;
}
// is the number (x) a prime number?
bool prime(int x) {
  for (int i = 2; i * i <= x; i++) {
    if (!(x % i)) {
      return false;
    }
  }
  return true;
}

double kyori(pair<int, int> f, pair<int, int> s) {
  double ans = 0;
  double t = fabs(f.first - s.first);
  double y = fabs(f.second - s.second);
  ans = sqrt(t * t + y * y);
  return ans;
}

// saidai-kouyakusuu
inline int gcd(int x, int y) {
  if (!y) {
    return x;
  }
  return gcd(y, x % y);
}

// Union-Find Tree

class Union_Find {
  vector<int> par;
  vector<int> rankmy;

public:
  Union_Find(int size) {
    par = vector<int>(size);
    rankmy = vector<int>(size);
    for (int i = 0; i < size; i++) {
      par[i] = i;
    }
  }

  int find(int x) {
    if (par[x] == x) {
      return x;
    }
    return par[x] = find(par[x]);
  }

  void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) {
      return;
    }
    if (rankmy[x] < rankmy[y]) {
      par[x] = y;
    } else {
      par[y] = x;
      if (rankmy[x] == rankmy[y]) {
        rankmy[x]++;
      }
    }
  }

  bool same(int x, int y) { return find(x) == find(y); }
};

// Union-Find-End

// SegTree
template <class T> class SegTree {
  int n;                       // 葉の数
  vector<T> data;              // データを格納するvector
  T def;                       // 初期値かつ単位元
  function<T(T, T)> operation; // 区間クエリで使う処理
  function<T(T, T)> update;    // 点更新で使う処理

  // 区間[a,b)の総和。ノードk=[l,r)に着目している。
  T _query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l)
      return def; // 交差しない
    if (a <= l && r <= b)
      return data[k]; // a,l,r,bの順で完全に含まれる
    else {
      T c1 = _query(a, b, 2 * k + 1, l, (l + r) / 2); // 左の子
      T c2 = _query(a, b, 2 * k + 2, (l + r) / 2, r); // 右の子
      return operation(c1, c2);
    }
  }

public:
  // _n:必要サイズ, _def:初期値かつ単位元, _operation:クエリ関数,
  // _update:更新関数
  SegTree(size_t _n, T _def, function<T(T, T)> _operation,
          function<T(T, T)> _update)
      : def(_def), operation(_operation), update(_update) {
    n = 1;
    while (n < _n) {
      n *= 2;
    }
    data = vector<T>(2 * n - 1, def);
  }

  // 場所i(0-indexed)の値をxで更新
  void change(int i, T x) {
    i += n - 1;
    data[i] = update(data[i], x);
    while (i > 0) {
      i = (i - 1) / 2;
      data[i] = operation(data[i * 2 + 1], data[i * 2 + 2]);
    }
  }

  // [a, b)の区間クエリを実行
  T query(int a, int b) { return _query(a, b, 0, 0, n); }

  // 添字でアクセス
  T operator[](int i) { return data[i + n - 1]; }
};

#define R_MIN ([](long long a, long long b) { return min(a, b); })
#define R_MAX ([](long long a, long long b) { return max(a, b); })
#define R_SUM ([](long long a, long long b) { return a + b; })

#define NORMAL_UPDATE ([](long long a, long long b) { return b; })
#define ADD_UPDATE ([](long long a, long long b) { return a + b; })
#define MINUS_UPDATE ([](long long a, long long b) { return a - b; }
// Seg-Tree-End

// dfs
// vector<int> v[100004];
// bool went[100004];
// void dfs(int x) {
//     went[x] = true;
//     for (int i = 0; i < (int)v[x].size(); i++) {
//         if (!went[v[x][i]]) {
//             dfs(v[x][i]);
//         }
//     }
// }

// number of keta
int keta(int x) {
  int ans = 0;
  while (x) {
    x /= 10;
    ans++;
  }
  return ans;
}

// sum of keta
int ketasum(int x) {
  int ans = 0;
  while (x) {
    ans += x % 10;
    x /= 10;
  }
  return ans;
}

inline int lcm(int x, int y) {
  int ans = x / gcd(x, y) * y;
  return ans;
}
int twobeki(int x) {
  int ans = 0;
  while (1) {
    if (!(x & 1)) {
      ans++;
      x /= 2;
    } else {
      break;
    }
  }
  return ans;
}

int kai(int x, int y) {
  int res = 1;
  for (int i = x - y + 1; i <= x; i++) {
    res *= i;
    res %= mod;
  }
  return res;
}

int comb(int x, int y) {
  if (y > x)
    return 0;
  return kai(x, y) * modpow(kai(y, y), mod - 2) % mod;
}

int fukugen(vector<int> l) {
  int ans = 0;
  for (int i = 0; i < (int)l.size(); i++) {
    ans *= 10;
    ans += l[i];
  }
  return ans;
}
int nanjyo(int n) {
  int ans = 0;
  while (n > 1) {
    ans++;
    n /= 2;
  }
  return ans;
}
bool intersect(pair<pair<int, int>, pair<int, int>> p1,
               pair<pair<int, int>, pair<int, int>> p2) {
  int men11 =
      (p2.first.first - p1.first.first) * (p2.second.second - p1.first.second) -
      (p2.second.first - p1.first.first) * (p2.first.second - p1.first.second);
  int men12 = (p2.first.first - p1.second.first) *
                  (p2.second.second - p1.second.second) -
              (p2.second.first - p1.second.first) *
                  (p2.first.second - p1.second.second);
  int men21 =
      (p1.first.first - p2.first.first) * (p1.second.second - p2.first.second) -
      (p1.second.first - p2.first.first) * (p1.first.second - p2.first.second);
  int men22 = (p1.first.first - p2.second.first) *
                  (p1.second.second - p2.second.second) -
              (p1.second.first - p2.second.first) *
                  (p1.first.second - p2.second.second);

  return ((signbit(men11)) ^ (signbit(men12))) &&
         ((signbit(men21)) ^ (signbit(men22)));
}
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;
}
void Yes() { cout << "Yes" << endl; }
void No() { cout << "No" << endl; }
void YES() { cout << "YES" << endl; }
void NO() { cout << "NO" << endl; }
#define rep(i, n) for (int i = 0; i < n; i++)
#define REP(i, n) for (int i = 1; i <= n; i++)
// Library-End
vector<int> v[100004];
bool went[100004], went2[100004], went3[100004], went4[100004];
int kyo[100004], kyo2[100004];
int n, m, a, b, ans, numf, nums;
void dfs(int x, int y) {
  kyo[x] = y;
  went[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (!went[v[x][i]]) {
      dfs(v[x][i], y + 1);
    }
  }
}
void ndfs(int x, int y) {
  kyo2[x] = y;
  went2[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (!went2[v[x][i]]) {
      ndfs(v[x][i], y + 1);
    }
  }
}
void dfs2(int x) {
  numf++;
  went3[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (v[x][i] == -100) {
      continue;
    }
    if (!went3[v[x][i]]) {
      dfs2(v[x][i]);
    }
  }
}
void ndfs2(int x) {
  nums++;
  went4[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (v[x][i] == -100) {
      continue;
    }
    if (!went4[v[x][i]]) {
      ndfs2(v[x][i]);
    }
  }
}

signed main() {
  cin >> n;
  rep(i, n - 1) {
    cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  dfs(1, 0);
  ndfs(n, 0);
  if (kyo[n] & 1) {
    vector<int> vec;
    REP(i, n) {
      if ((kyo[i] == kyo[n] / 2 && kyo2[i] == kyo2[1] / 2 + 1) ||
          (kyo2[i] == kyo2[1] / 2 && kyo[i] == kyo[n] / 2 + 1)) {
        vec.push_back(i);
      }
    }
    assert(vec.size() <= 2);
    rep(i, v[vec[0]].size()) {
      if (v[vec[0]][i] == vec[1]) {
        v[vec[0]][i] = -100;
      }
    }
    rep(i, v[vec[1]].size()) {
      if (v[vec[1]][i] == vec[0]) {
        v[vec[1]][i] = -100;
      }
    }
  } else {
    vector<int> vec;
    REP(i, n) {
      if (kyo[i] == kyo2[i] ||
          (kyo2[i] == kyo2[1] / 2 - 1 && kyo[i] == kyo[n] / 2 + 1)) {
        vec.push_back(i);
      }
    }
    assert(vec.size() <= 2);
    rep(i, v[vec[0]].size()) {
      if (v[vec[0]][i] == vec[1]) {
        v[vec[0]][i] = -100;
      }
    }
    rep(i, v[vec[1]].size()) {
      if (v[vec[1]][i] == vec[0]) {
        v[vec[1]][i] = -100;
      }
    }
  }
  dfs2(1);
  ndfs2(n);
  if (numf > nums) {
    cout << "Fennec" << endl;
  } else {
    cout << "Snuke" << endl;
  }
}


Fixed submission:
#include <bits/stdc++.h>

#define f(i, n) for (int i = 0; i < (n); i++)

#define inf (int)(3e18)
#define int long long
#define mod (int)(1000000007)

#define intt long long

using namespace std;

// Library
// モッドパウ
int modpow(int x, int y, int m = mod) {
  int res = 1;
  while (y) {
    if (y % 2) {
      res *= x;
      res %= m;
    }
    x = x * x % mod;
    y /= 2;
  }
  return res;
}

int mypow(int x, int y) {
  int res = 1;
  while (y) {
    if (y % 2) {
      res *= x;
    }
    x = x * x;
    y /= 2;
  }
  return res;
}
// is the number (x) a prime number?
bool prime(int x) {
  for (int i = 2; i * i <= x; i++) {
    if (!(x % i)) {
      return false;
    }
  }
  return true;
}

double kyori(pair<int, int> f, pair<int, int> s) {
  double ans = 0;
  double t = fabs(f.first - s.first);
  double y = fabs(f.second - s.second);
  ans = sqrt(t * t + y * y);
  return ans;
}

// saidai-kouyakusuu
inline int gcd(int x, int y) {
  if (!y) {
    return x;
  }
  return gcd(y, x % y);
}

// Union-Find Tree

class Union_Find {
  vector<int> par;
  vector<int> rankmy;

public:
  Union_Find(int size) {
    par = vector<int>(size);
    rankmy = vector<int>(size);
    for (int i = 0; i < size; i++) {
      par[i] = i;
    }
  }

  int find(int x) {
    if (par[x] == x) {
      return x;
    }
    return par[x] = find(par[x]);
  }

  void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) {
      return;
    }
    if (rankmy[x] < rankmy[y]) {
      par[x] = y;
    } else {
      par[y] = x;
      if (rankmy[x] == rankmy[y]) {
        rankmy[x]++;
      }
    }
  }

  bool same(int x, int y) { return find(x) == find(y); }
};

// Union-Find-End

// SegTree
template <class T> class SegTree {
  int n;                       // 葉の数
  vector<T> data;              // データを格納するvector
  T def;                       // 初期値かつ単位元
  function<T(T, T)> operation; // 区間クエリで使う処理
  function<T(T, T)> update;    // 点更新で使う処理

  // 区間[a,b)の総和。ノードk=[l,r)に着目している。
  T _query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l)
      return def; // 交差しない
    if (a <= l && r <= b)
      return data[k]; // a,l,r,bの順で完全に含まれる
    else {
      T c1 = _query(a, b, 2 * k + 1, l, (l + r) / 2); // 左の子
      T c2 = _query(a, b, 2 * k + 2, (l + r) / 2, r); // 右の子
      return operation(c1, c2);
    }
  }

public:
  // _n:必要サイズ, _def:初期値かつ単位元, _operation:クエリ関数,
  // _update:更新関数
  SegTree(size_t _n, T _def, function<T(T, T)> _operation,
          function<T(T, T)> _update)
      : def(_def), operation(_operation), update(_update) {
    n = 1;
    while (n < _n) {
      n *= 2;
    }
    data = vector<T>(2 * n - 1, def);
  }

  // 場所i(0-indexed)の値をxで更新
  void change(int i, T x) {
    i += n - 1;
    data[i] = update(data[i], x);
    while (i > 0) {
      i = (i - 1) / 2;
      data[i] = operation(data[i * 2 + 1], data[i * 2 + 2]);
    }
  }

  // [a, b)の区間クエリを実行
  T query(int a, int b) { return _query(a, b, 0, 0, n); }

  // 添字でアクセス
  T operator[](int i) { return data[i + n - 1]; }
};

#define R_MIN ([](long long a, long long b) { return min(a, b); })
#define R_MAX ([](long long a, long long b) { return max(a, b); })
#define R_SUM ([](long long a, long long b) { return a + b; })

#define NORMAL_UPDATE ([](long long a, long long b) { return b; })
#define ADD_UPDATE ([](long long a, long long b) { return a + b; })
#define MINUS_UPDATE ([](long long a, long long b) { return a - b; }
// Seg-Tree-End

// dfs
// vector<int> v[100004];
// bool went[100004];
// void dfs(int x) {
//     went[x] = true;
//     for (int i = 0; i < (int)v[x].size(); i++) {
//         if (!went[v[x][i]]) {
//             dfs(v[x][i]);
//         }
//     }
// }

// number of keta
int keta(int x) {
  int ans = 0;
  while (x) {
    x /= 10;
    ans++;
  }
  return ans;
}

// sum of keta
int ketasum(int x) {
  int ans = 0;
  while (x) {
    ans += x % 10;
    x /= 10;
  }
  return ans;
}

inline int lcm(int x, int y) {
  int ans = x / gcd(x, y) * y;
  return ans;
}
int twobeki(int x) {
  int ans = 0;
  while (1) {
    if (!(x & 1)) {
      ans++;
      x /= 2;
    } else {
      break;
    }
  }
  return ans;
}

int kai(int x, int y) {
  int res = 1;
  for (int i = x - y + 1; i <= x; i++) {
    res *= i;
    res %= mod;
  }
  return res;
}

int comb(int x, int y) {
  if (y > x)
    return 0;
  return kai(x, y) * modpow(kai(y, y), mod - 2) % mod;
}

int fukugen(vector<int> l) {
  int ans = 0;
  for (int i = 0; i < (int)l.size(); i++) {
    ans *= 10;
    ans += l[i];
  }
  return ans;
}
int nanjyo(int n) {
  int ans = 0;
  while (n > 1) {
    ans++;
    n /= 2;
  }
  return ans;
}
bool intersect(pair<pair<int, int>, pair<int, int>> p1,
               pair<pair<int, int>, pair<int, int>> p2) {
  int men11 =
      (p2.first.first - p1.first.first) * (p2.second.second - p1.first.second) -
      (p2.second.first - p1.first.first) * (p2.first.second - p1.first.second);
  int men12 = (p2.first.first - p1.second.first) *
                  (p2.second.second - p1.second.second) -
              (p2.second.first - p1.second.first) *
                  (p2.first.second - p1.second.second);
  int men21 =
      (p1.first.first - p2.first.first) * (p1.second.second - p2.first.second) -
      (p1.second.first - p2.first.first) * (p1.first.second - p2.first.second);
  int men22 = (p1.first.first - p2.second.first) *
                  (p1.second.second - p2.second.second) -
              (p1.second.first - p2.second.first) *
                  (p1.first.second - p2.second.second);

  return ((signbit(men11)) ^ (signbit(men12))) &&
         ((signbit(men21)) ^ (signbit(men22)));
}
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;
}
void Yes() { cout << "Yes" << endl; }
void No() { cout << "No" << endl; }
void YES() { cout << "YES" << endl; }
void NO() { cout << "NO" << endl; }
#define rep(i, n) for (int i = 0; i < n; i++)
#define REP(i, n) for (int i = 1; i <= n; i++)
// Library-End
vector<int> v[100004];
bool went[100004], went2[100004], went3[100004], went4[100004];
int kyo[100004], kyo2[100004];
int n, m, a, b, ans, numf, nums;
void dfs(int x, int y) {
  kyo[x] = y;
  went[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (!went[v[x][i]]) {
      dfs(v[x][i], y + 1);
    }
  }
}
void ndfs(int x, int y) {
  kyo2[x] = y;
  went2[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (!went2[v[x][i]]) {
      ndfs(v[x][i], y + 1);
    }
  }
}
void dfs2(int x) {
  numf++;
  went3[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (v[x][i] == -100) {
      continue;
    }
    if (!went3[v[x][i]]) {
      dfs2(v[x][i]);
    }
  }
}
void ndfs2(int x) {
  nums++;
  went4[x] = true;
  for (int i = 0; i < (int)v[x].size(); i++) {
    if (v[x][i] == -100) {
      continue;
    }
    if (!went4[v[x][i]]) {
      ndfs2(v[x][i]);
    }
  }
}

signed main() {
  cin >> n;
  rep(i, n - 1) {
    cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  dfs(1, 0);
  ndfs(n, 0);
  REP(i, n) {
    if (kyo[i] <= kyo2[i]) {
      numf++;
    } else {
      nums++;
    }
  }
  if (numf > nums) {
    cout << "Fennec" << endl;
  } else {
    cout << "Snuke" << endl;
  }
}