Language: C++

#include "bits/stdc++.h"
#define FOR(i, n, m) for(ll i = n; i < (int)m; i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define pb push_back
using namespace std;
using ll = std::int_fast64_t;
using P = pair<ll, ll>;
constexpr ll inf = 1000000000;
constexpr ll mod = 1000000007;
constexpr long double eps = 1e-15;
template<typename T1, typename T2>
ostream& operator<<(ostream& os, pair<T1, T2> p) {
    os << to_string(p.first) << " " << to_string(p.second);
    return os;
}
template<typename T>
ostream& operator<<(ostream& os, vector<T>& v) {
    REP(i, v.size()) {
        if(i) os << " ";
        os << to_string(v[i]);
    }
    return os;
}

struct modint {
    ll n;
public:
    modint(const ll n = 0) : n((n % mod + mod) % mod) {}
    static modint pow(modint a, int m) {
        modint r = 1;
        while(m > 0) {
            if(m & 1) { r *= a; }
            a = (a * a); m /= 2;
        }
        return r;
    }
    modint &operator++() { *this += 1; return *this; }
    modint &operator--() { *this -= 1; return *this; }
    modint operator++(int) { modint ret = *this; *this += 1; return ret; }
    modint operator--(int) { modint ret = *this; *this -= 1; return ret; }
    modint operator~() const { return (this -> pow(n, mod - 2)); } // inverse
    friend bool operator==(const modint& lhs, const modint& rhs) {
        return lhs.n == rhs.n;
    }
    friend bool operator<(const modint& lhs, const modint& rhs) {
        return lhs.n < rhs.n;
    }
    friend bool operator>(const modint& lhs, const modint& rhs) {
        return lhs.n > rhs.n;
    }
    friend modint &operator+=(modint& lhs, const modint& rhs) {
        lhs.n += rhs.n;
        if (lhs.n >= mod) lhs.n -= mod;
        return lhs;
    }
    friend modint &operator-=(modint& lhs, const modint& rhs) {
        lhs.n -= rhs.n;
        if (lhs.n < 0) lhs.n += mod;
        return lhs;
    }
    friend modint &operator*=(modint& lhs, const modint& rhs) {
        lhs.n = (lhs.n * rhs.n) % mod;
        return lhs;
    }
    friend modint &operator/=(modint& lhs, const modint& rhs) {
        lhs.n = (lhs.n * (~rhs).n) % mod;
        return lhs;
    }
    friend modint operator+(const modint& lhs, const modint& rhs) {
        return modint(lhs.n + rhs.n);
    }
    friend modint operator-(const modint& lhs, const modint& rhs) {
        return modint(lhs.n - rhs.n);
    }
    friend modint operator*(const modint& lhs, const modint& rhs) {
        return modint(lhs.n * rhs.n);
    }
    friend modint operator/(const modint& lhs, const modint& rhs) {
        return modint(lhs.n * (~rhs).n);
    }
};
istream& operator>>(istream& is, modint m) { is >> m.n; return is; }
ostream& operator<<(ostream& os, modint m) { os << m.n; return os; }

#define MAX_N 3030303
long long extgcd(long long a, long long b, long long& x, long long& y) {
    long long d = a;
    if (b != 0) {
        d = extgcd(b, a % b, y, x);
        y -= (a / b) * x;
    } else {
        x = 1; y = 0;
    }
    return d;
}
long long mod_inverse(long long a, long long m) {
    long long x, y;
    if(extgcd(a, m, x, y) == 1) return (m + x % m) % m;
    else return -1;
}
vector<long long> fact(MAX_N+1, inf);
long long mod_fact(long long n, long long& e) {
    if(fact[0] == inf) {
        fact[0]=1;
        if(MAX_N != 0) fact[1]=1;
        for(ll i = 2; i <= MAX_N; ++i) {
            fact[i] = (fact[i-1] * i) % mod;
        }
    }
    e = 0;
    if(n == 0) return 1;
    long long res = mod_fact(n / mod, e);
    e += n / mod;
    if((n / mod) % 2 != 0) return (res * (mod - fact[n % mod])) % mod;
    return (res * fact[n % mod]) % mod;
}
// return nCk
long long mod_comb(long long n, long long k) {
    if(n < 0 || k < 0 || n < k) return 0;
    long long e1, e2, e3;
    long long a1 = mod_fact(n, e1), a2 = mod_fact(k, e2), a3 = mod_fact(n - k, e3);
    if(e1 > e2 + e3) return 0;
    return (a1 * mod_inverse((a2 * a3) % mod, mod)) % mod;
}

using mi = modint;

mi dp1[3030][3030][2][2];
mi dp2[3030][3030][2];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    if(n == 1) {
        mi ans = 2;
        REP(i, n) ans *= 2;
        cout << ans << endl;
        return 0;
    }
    for(int i = 0; i <= m; i++) for(int j = 0; j <= n; j++) {
        REP(k, 2) REP(l, 2) {
            if(i == 0) {
                if(k && l) dp1[i][j][k][l] = 1;
                else dp1[i][j][k][l] = 0;
            } else {
                if(j) {
                    if(j - 1 == 0) dp1[i][j][k][l] +=
                        dp1[i - 1][j - 1][1][l] + dp1[i - 1][j][1][l];
                    else dp1[i][j][k][l] +=
                        dp1[i - 1][j - 1][k][l] + dp1[i - 1][j][k][l];
                }
                if(j < n) {
                    if(j + 1 == n) dp1[i][j][k][l] +=
                        dp1[i - 1][j + 1][k][1] + dp1[i - 1][j][k][1];
                    else dp1[i][j][k][l] +=
                        dp1[i - 1][j + 1][k][l] + dp1[i - 1][j][k][l];
                }
            }
        }
    }
    for(int i = 0; i <= m; i++) for(int j = 0; j <= n - 1; j++) {
        REP(k, 2) {
            if(i == 0) {
                if(k) dp2[i][j][k] = 1;
                else dp2[i][j][k] = 0;
            } else {
                if(j) {
                    if(j - 1 == 0) dp2[i][j][k] +=
                        dp2[i - 1][j - 1][1] + dp2[i - 1][j][1];
                    else dp2[i][j][k] +=
                        dp2[i - 1][j - 1][k] + dp2[i - 1][j][k];
                }
                if(j < n - 1) {
                    dp2[i][j][k] += dp2[i - 1][j + 1][k] + dp2[i - 1][j][k];
                }
            }
        }
    }
    mi ans = 0;
    REP(i, n + 1) {
        if(i == 0) ans += dp1[m][i][1][0];
        else if(i == n) ans += dp1[m][i][0][1];
        else ans += dp1[m][i][0][0];
    }#include <iostream>
#include <vector>
#include <queue>
#include <math.h>
#include <set>
#define FOR(i, n, m) for(ll i = n; i < (int)m; i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define pb push_back
using namespace std;
using ll = std::int_fast64_t;
using P = pair<ll, ll>;
constexpr ll inf = 1000000000;
constexpr ll mod = 1000000007;
constexpr long double eps = 1e-15;
template<typename T1, typename T2>
ostream& operator<<(ostream& os, pair<T1, T2> p) {
    os << to_string(p.first) << " " << to_string(p.second);
    return os;
}
template<typename T>
ostream& operator<<(ostream& os, vector<T>& v) {
    REP(i, v.size()) {
        if(i) os << " ";
        os << to_string(v[i]);
    }
    return os;
}

struct modint {
    ll n;
public:
    modint(const ll n = 0) : n((n % mod + mod) % mod) {}
    static modint pow(modint a, int m) {
        modint r = 1;
        while(m > 0) {
            if(m & 1) { r *= a; }
            a = (a * a); m /= 2;
        }
        return r;
    }
    modint &operator++() { *this += 1; return *this; }
    modint &operator--() { *this -= 1; return *this; }
    modint operator++(int) { modint ret = *this; *this += 1; return ret; }
    modint operator--(int) { modint ret = *this; *this -= 1; return ret; }
    modint operator~() const { return (this -> pow(n, mod - 2)); } // inverse
    friend bool operator==(const modint& lhs, const modint& rhs) {
        return lhs.n == rhs.n;
    }
    friend bool operator<(const modint& lhs, const modint& rhs) {
        return lhs.n < rhs.n;
    }
    friend bool operator>(const modint& lhs, const modint& rhs) {
        return lhs.n > rhs.n;
    }
    friend modint &operator+=(modint& lhs, const modint& rhs) {
        lhs.n += rhs.n;
        if (lhs.n >= mod) lhs.n -= mod;
        return lhs;
    }
    friend modint &operator-=(modint& lhs, const modint& rhs) {
        lhs.n -= rhs.n;
        if (lhs.n < 0) lhs.n += mod;
        return lhs;
    }
    friend modint &operator*=(modint& lhs, const modint& rhs) {
        lhs.n = (lhs.n * rhs.n) % mod;
        return lhs;
    }
    friend modint &operator/=(modint& lhs, const modint& rhs) {
        lhs.n = (lhs.n * (~rhs).n) % mod;
        return lhs;
    }
    friend modint operator+(const modint& lhs, const modint& rhs) {
        return modint(lhs.n + rhs.n);
    }
    friend modint operator-(const modint& lhs, const modint& rhs) {
        return modint(lhs.n - rhs.n);
    }
    friend modint operator*(const modint& lhs, const modint& rhs) {
        return modint(lhs.n * rhs.n);
    }
    friend modint operator/(const modint& lhs, const modint& rhs) {
        return modint(lhs.n * (~rhs).n);
    }
};
istream& operator>>(istream& is, modint m) { is >> m.n; return is; }
ostream& operator<<(ostream& os, modint m) { os << m.n; return os; }

#define MAX_N 3030303
long long extgcd(long long a, long long b, long long& x, long long& y) {
    long long d = a;
    if (b != 0) {
        d = extgcd(b, a % b, y, x);
        y -= (a / b) * x;
    } else {
        x = 1; y = 0;
    }
    return d;
}
long long mod_inverse(long long a, long long m) {
    long long x, y;
    if(extgcd(a, m, x, y) == 1) return (m + x % m) % m;
    else return -1;
}
vector<long long> fact(MAX_N+1, inf);
long long mod_fact(long long n, long long& e) {
    if(fact[0] == inf) {
        fact[0]=1;
        if(MAX_N != 0) fact[1]=1;
        for(ll i = 2; i <= MAX_N; ++i) {
            fact[i] = (fact[i-1] * i) % mod;
        }
    }
    e = 0;
    if(n == 0) return 1;
    long long res = mod_fact(n / mod, e);
    e += n / mod;
    if((n / mod) % 2 != 0) return (res * (mod - fact[n % mod])) % mod;
    return (res * fact[n % mod]) % mod;
}
// return nCk
long long mod_comb(long long n, long long k) {
    if(n < 0 || k < 0 || n < k) return 0;
    long long e1, e2, e3;
    long long a1 = mod_fact(n, e1), a2 = mod_fact(k, e2), a3 = mod_fact(n - k, e3);
    if(e1 > e2 + e3) return 0;
    return (a1 * mod_inverse((a2 * a3) % mod, mod)) % mod;
}

using mi = modint;

mi dp1[3030][3030][2][2];
mi dp2[3030][3030][2];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    if(n == 1) {
        mi ans = 2;
        REP(i, n) ans *= 2;
        cout << ans << endl;
        return 0;
    }
    for(int i = 0; i <= m; i++) for(int j = 0; j <= n; j++) {
        REP(k, 2) REP(l, 2) {
            if(i == 0) {
                if(k && l) dp1[i][j][k][l] = 1;
                else dp1[i][j][k][l] = 0;
            } else {
                if(j) {
                    if(j - 1 == 0) dp1[i][j][k][l] +=
                        dp1[i - 1][j - 1][1][l] + dp1[i - 1][j][1][l];
                    else dp1[i][j][k][l] +=
                        dp1[i - 1][j - 1][k][l] + dp1[i - 1][j][k][l];
                }
                if(j < n) {
                    if(j + 1 == n) dp1[i][j][k][l] +=
                        dp1[i - 1][j + 1][k][1] + dp1[i - 1][j][k][1];
                    else dp1[i][j][k][l] +=
                        dp1[i - 1][j + 1][k][l] + dp1[i - 1][j][k][l];
                }
            }
        }
    }
    for(int i = 0; i <= m; i++) for(int j = 0; j <= n - 1; j++) {
        REP(k, 2) {
            if(i == 0) {
                if(k) dp2[i][j][k] = 1;
                else dp2[i][j][k] = 0;
            } else {
                if(j) {
                    if(j - 1 == 0) dp2[i][j][k] +=
                        dp2[i - 1][j - 1][1] + dp2[i - 1][j][1];
                    else dp2[i][j][k] +=
                        dp2[i - 1][j - 1][k] + dp2[i - 1][j][k];
                }
                if(j < n - 1) {
                    dp2[i][j][k] += dp2[i - 1][j + 1][k] + dp2[i - 1][j][k];
                }
            }
        }
    }
    mi ans = 0;
    REP(i, n + 1) {
        if(i == 0) ans += dp1[m][i][1][0];
        else if(i == n) ans += dp1[m][i][0][1];
        else ans += dp1[m][i][0][0];
    }
    REP(i, n + 1) {
        if(i == 0) ans += dp2[m][i][1];
        else ans += dp2[m][i][0];
    }
    cout << ans << endl;
    return 0;
}

    REP(i, n + 1) {
        if(i == 0) ans += dp2[m][i][1];
        else ans += dp2[m][i][0];
    }
    cout << ans << endl;
    return 0;
}


Compiler output:
a.cc:187:6: error: stray '#' in program
  187 |     }#include <iostream>
      |      ^
a.cc: In function 'int main()':
a.cc:187:7: error: 'include' was not declared in this scope
  187 |     }#include <iostream>
      |       ^~~~~~~
a.cc:187:24: error: expected primary-expression before '>' token
  187 |     }#include <iostream>
      |                        ^
In file included from a.cc:190:
/usr/include/c++/14/math.h:38:1: error: expected primary-expression before 'using'
   38 | using std::abs;
      | ^~~~~
a.cc:202:1: error: a template declaration cannot appear at block scope
  202 | template<typename T1, typename T2>
      | ^~~~~~~~
a.cc:233:17: error: cannot define friend function 'operator==' in a local class definition
  233 |     friend bool operator==(const modint& lhs, const modint& rhs) {
      |                 ^~~~~~~~
a.cc:233:17: error: 'bool main()::modint::operator==(const main()::modint&, const main()::modint&)' must have exactly one argument
a.cc:236:17: error: cannot define friend function 'operator<' in a local class definition
  236 |     friend bool operator<(const modint& lhs, const modint& rhs) {
      |                 ^~~~~~~~
a.cc:236:17: error: 'bool main()::modint::operator<(const main()::modint&, const main()::modint&)' must have exactly one argument
a.cc:239:17: error: cannot define friend function 'operator>' in a local class definition
  239 |     friend bool operator>(const modint& lhs, const modint& rhs) {
      |                 ^~~~~~~~
a.cc:239:17: error: 'bool main()::modint::operator>(const main()::modint&, const main()::modint&)' must have exactly one argument
a.cc:242:20: error: cannot define friend function 'operator+=' in a local class definition
  242 |     friend modint &operator+=(modint& lhs, const modint& rhs) {
      |                    ^~~~~~~~
a.cc:242:20: error: 'main()::modint& main()::modint::operator+=(main()::modint&, const main()::modint&)' must have exactly one argument
a.cc:247:20: error: cannot define friend function 'operator-=' in a local class definition
  247 |     friend modint &operator-=(modint& lhs, const modint& rhs) {
      |                    ^~~~~~~~
a.cc:247:20: error: 'main()::modint& main()::modint::operator-=(main()::modint&, const main()::modint&)' must have exactly one argument
a.cc:252:20: error: cannot define friend function 'operator*=' in a local class definition
  252 |     friend modint &operator*=(modint& lhs, const modint& rhs) {
      |                    ^~~~~~~~
a.cc:252:20: error: 'main()::modint& main()::modint::operator*=(main()::modint&, const main()::modint&)' must have exactly one argument
a.cc:256:20: error: cannot define friend function 'operator/=' in a local class definition
  256 |     friend modint &operator/=(modint& lhs, const modint& rhs) {
      |                    ^~~~~~~~
a.cc:256:20: error: 'main()::modint& main()::modint::operator/=(main()::modint&, const main()::modint&)' must have exactly one argument
a.cc:260:19: error: cannot define friend function 'operator+' in a local class definition
  260 |     friend modint operator+(const modint& lhs, const modint& rhs) {
      |                   ^~~~~~~~
a.cc:260:19: error: 'main()::modint main()::modint::operator+(const main()::modint&, const main()::modint&)' must have either zero or one argument
a.cc:263:19: error: cannot define friend function 'operator-' in a local class definition
  263 |     friend modint operator-(const modint& lhs, const modint& rhs) {
      |                   ^~~~~~~~
a.cc:263:19: error: 'main()::modint main()::modint::operator-(const main()::modint&, const main()::modint&)' must have either zero or one argument
a.cc:266:19: error: cannot define friend function 'operator*' in a local class definition
  266 |     friend modint operator*(const modint& lhs, const modint& rhs) {
      |                   ^~~~~~~~
a.cc:266:19: error: 'main()::modint main()::modint::operator*(const main()::modint&, const main()::modint&)' must have either zero or one argument
a.cc:269:19: error: cannot define friend function 'operator/' in a local class definition
  269 |     friend modint operator/(const modint& lhs, const modint& rhs) {
      |                   ^~~~~~~~
a.cc:269:19: error: 'main()::modint main()::modint::operator/(const main()::modint&, const main()::modint&)' must have exactly one argument
a.cc: In static member function 'static main()::modint main()::modint::pow(main()::modint, int)':
a.cc:223:27: error: no match for 'operator*=' (operand types are 'main()::modint' and 'main()::modint')
  223 |             if(m & 1) { r *= a; }
      |                         ~~^~~~
a.cc:224:20: error: no match for 'operator*' (operand types are 'main()::modint' and 'main()::modint')
  224 |             a = (a * a); m /= 2;
      |                  ~ ^ ~
      |                  |   |
      |                  |   main()::modint
      |                  main()::modint
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:1:
/usr/include/c++/14/complex:400:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const complex<_Tp>&)'
  400 |     operator*(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:400:5: note:   template argument deduction/substitution failed:
a.cc:224:22: note:   'main()::modint' is not derived from 'const std::complex<_Tp>'
  224 |             a = (a * a); m /= 2;
      |                      ^
/usr/include/c++/14/complex:409:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const _Tp&)'
  409 |     operator*(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:409:5: note:   template argument deduction/substitution failed:
a.cc:224:22: note:   'main()::modint' is not derived from 'const std::complex<_Tp>'
  224 |             a = (a * a); m /= 2;
      |                      ^
/usr/include/c++/14/complex:418:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const _Tp&, const complex<_Tp>&)'
  418 |     operator*(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:418:5: note:   template argument deduction/substitution failed:
a.cc:224:22: note:   'main()::modint' is not derived from 'const std::complex<_Tp>'
  224 |             a = (a * a); m /= 2;
      |                      ^
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:224:22: note:   'main()::modint' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  224 |             a = (a * a); m /= 2;
      |                      ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:224:22: note:   'main()::modint' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  224 |             a = (a * a); m /= 2;
      |                      ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:224:22: note:   'main()::modint' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  224 |             a = (a * a); m /= 2;
      |                      ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:224:22: note:   'main()::modint' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  224 |             a = (a * a); m /= 2;
      |                      ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BIN