func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long mod = 1e9 + 7;   long long qsm(long long a, int b) {     a %= mod;     long long ret = 1;     while (b) {       if (b & 1) ret = ret * a % mod;       b >>= 1;       a = a * a % mod;     }     return ret;   }   long long a[220000], b[220000], f[220000];   int main() {     long long n;     scanf( %lld , &n);     for (int i = 0; i < n; i++) scanf( %lld , &a[i]), b[i] = a[i];     if (n == 1) {       printf( %lld n , a[0]);       return 0;     }     if (n & 1) {       n--;       int o = 0;       for (int i = 0; i < n; i++) {         if (!o)           b[i] = (a[i] + a[i + 1]) % mod;         else           b[i] = (a[i] - a[i + 1]) % mod;         o ^= 1;       }     }     f[0] = 1;     long long m = n / 2 - 1;     for (int i = 1; i <= m; i++) f[i] = f[i - 1] * i % mod;     long long ans1 = 0, ans2 = 0;     for (int i = 0; i <= m; i++) {       ans1 = (ans1 + f[m] * qsm(f[i] * f[m - i], mod - 2) % mod * b[i * 2]) % mod;       ans2 = (ans2 + f[m] * qsm(f[i] * f[m - i], mod - 2) % mod * b[i * 2 + 1]) %              mod;     }     long long ans;     if ((n * (n - 1) / 2) & 1)       ans = ((ans1 + ans2) % mod + mod) % mod;     else       ans = ((ans1 - ans2) % mod + mod) % mod;     printf( %lld n , ans);     return 0;   }   