func_code_string: #include <bits/stdc++.h>   using namespace std;   int n;   const int maxn = 4001;   long long dp[maxn], c[maxn][maxn], s[maxn][maxn], sum[maxn];   long long pow(int k) {     if (k == 0) return 1LL;     if (k == 1) return 2LL;     long long ans = pow(k >> 1);     ans *= ans;     if (k % 2) ans *= 2LL;     return (ans % 1000000007);   }   void pre() {     c[0][0] = c[1][0] = c[1][1] = 1LL;     s[1][0] = 0;     s[1][1] = 1LL;     for (int i = 2; i <= n; i++) {       c[i][0] = 1LL;       s[i][0] = 0;       for (int j = 1; j <= i; j++) {         c[i][j] = (c[i - 1][j] + c[i - 1][j - 1]) % 1000000007;         s[i][j] = (j * s[i - 1][j] + s[i - 1][j - 1]) % 1000000007;       }     }     for (int i = 1; i <= n; i++)       for (int j = 0; j <= i; j++) sum[i] = (sum[i] + s[i][j]) % 1000000007;   }   int main() {     cin >> n;     pre();     dp[1] = 1;     dp[2] = 3;     for (int i = 3; i <= n; i++) {       dp[i] = 1;       for (int j = 1; j <= n - 1; j++)         dp[i] = (dp[i] + (dp[j] + sum[j]) * c[i - 1][j]) % 1000000007;     }     if (dp[n] < 0) dp[n] += 1000000007;     printf( %I64d n , dp[n]);     return 0;   }   