func_code_string: #include <bits/stdc++.h>   const int inf = 0x3f3f3f3f, Inf = 0x7fffffff;   const long long INF = 0x3f3f3f3f3f3f3f3f;   __inline__ __attribute__((always_inline)) unsigned int rnd() {     static unsigned int seed = 416;     return seed ^= seed >> 5, seed ^= seed << 17, seed ^= seed >> 13;   }   template <typename _Tp>   _Tp gcd(const _Tp &a, const _Tp &b) {     return (!b) ? a : gcd(b, a % b);   }   template <typename _Tp>   __inline__ __attribute__((always_inline)) _Tp abs(const _Tp &a) {     return a >= 0 ? a : -a;   }   template <typename _Tp>   __inline__ __attribute__((always_inline)) _Tp max(const _Tp &a, const _Tp &b) {     return a < b ? b : a;   }   template <typename _Tp>   __inline__ __attribute__((always_inline)) _Tp min(const _Tp &a, const _Tp &b) {     return a < b ? a : b;   }   template <typename _Tp>   __inline__ __attribute__((always_inline)) void chmax(_Tp &a, const _Tp &b) {     (a < b) && (a = b);   }   template <typename _Tp>   __inline__ __attribute__((always_inline)) void chmin(_Tp &a, const _Tp &b) {     (b < a) && (a = b);   }   template <typename _Tp>   __inline__ __attribute__((always_inline)) void read(_Tp &x) {     char ch(getchar());     bool f(false);     while (ch < 48 || ch > 57) f |= ch == 45, ch = getchar();     x = ch & 15, ch = getchar();     while (ch >= 48 && ch <= 57)       x = (((x << 2) + x) << 1) + (ch & 15), ch = getchar();     if (f) x = -x;   }   template <typename _Tp, typename... Args>   __inline__ __attribute__((always_inline)) void read(_Tp &t, Args &...args) {     read(t);     read(args...);   }   template <typename _Tp, typename... Args>   __inline__ __attribute__((always_inline)) _Tp min(const _Tp &a, const _Tp &b,                                                     const Args &...args) {     return a < b ? min(a, args...) : min(b, args...);   }   template <typename _Tp, typename... Args>   __inline__ __attribute__((always_inline)) _Tp max(const _Tp &a, const _Tp &b,                                                     const Args &...args) {     return a < b ? max(b, args...) : max(a, args...);   }   __inline__ __attribute__((always_inline)) int read_str(char *s) {     char ch(getchar());     while (ch ==     || ch ==   r  || ch ==   n ) ch = getchar();     char *tar = s;     *tar = ch, ch = getchar();     while (ch !=     && ch !=   r  && ch !=   n  && ch != EOF)       *(++tar) = ch, ch = getchar();     return tar - s + 1;   }   const int N = 4000005;   const int mod = 998244353;   template <typename _Tp1, typename _Tp2>   __inline__ __attribute__((always_inline)) void add(_Tp1 &a, _Tp2 b) {     (a += b) >= mod && (a -= mod);   }   template <typename _Tp1, typename _Tp2>   __inline__ __attribute__((always_inline)) void sub(_Tp1 &a, _Tp2 b) {     (a -= b) < 0 && (a += mod);   }   long long ksm(long long a, long long b = mod - 2) {     long long res = 1;     while (b) {       if (b & 1) res = res * a % mod;       a = a * a % mod, b >>= 1;     }     return res;   }   long long fac[N], inv[N], ifac[N];   void init() {     fac[0] = fac[1] = inv[0] = inv[1] = ifac[0] = ifac[1] = 1;     for (int i = 2; i < N; ++i) {       fac[i] = fac[i - 1] * i % mod;       inv[i] = inv[mod % i] * (mod - mod / i) % mod;       ifac[i] = ifac[i - 1] * inv[i] % mod;     }   }   __inline__ __attribute__((always_inline)) long long C(int n, int m) {     if (n < m) return 0;     return fac[n] * ifac[m] % mod * ifac[n - m] % mod;   }   long long f[N];   long long s1[N], s2[N], s3[N];   int main() {     init();     long long n, m;     read(n, m);     for (int i = 0; i <= n; ++i) {       if (i) s1[i] = s1[i - 1];       add(s1[i], fac[m + i - 1] * ifac[i] % mod);       if (i) s2[i] = s2[i - 1], add(s2[i], fac[m + i - 1] * ifac[i - 1] % mod);       long long _ = m * fac[i] % mod * fac[n - i] % mod * ifac[n + m] % mod;       long long tmp = _ * C(n + m + 1, m + i + 1) % mod *                       (s1[i] * (i + 1) % mod - s2[i] + mod) % mod;       long long coef =           (mod + 1 -            _ * C(n + m, m + i) % mod * ifac[i] % mod * fac[m + i - 1] % mod);       f[i] = (tmp + _ * C(n + m, m + i) % mod * s3[i] % mod) * ksm(coef) % mod;       s3[i + 1] = s3[i],              add(s3[i + 1], fac[m + i - 1] * ifac[i] % mod * f[i] % mod);     }     printf( %lld n , f[n]);     return 0;   }   