func_code_string: #include <bits/stdc++.h>   using namespace std;   long long f[2][200500], g[2][200500], sf[2][200500], sg[2][200500], ans;   int a, b, k, t;   const long long MOD = 1000000007;   int main() {     scanf( %d%d%d%d , &a, &b, &k, &t);     f[0][a + 100210] = 1;     g[0][b + 100210] = 1;     for (int j = -100000; j <= 100100; j++) {       sf[0][j + 100210] = (sf[0][j + 100209] + f[0][j + 100210]) % MOD;       sg[0][j + 100210] = (sg[0][j + 100209] + g[0][j + 100210]) % MOD;     }     for (int i = 1; i <= t; i++) {       for (int j = -100000; j <= 100100; j++) {         f[i & 1][j + 100210] =             (sf[(i - 1) & 1][min(100210 + a + k * i, j + k + 100210)] -              sf[(i - 1) & 1][max(100209 + a - k * i, j - k + 100209)]) %             MOD;         if (f[i & 1][j + 100210] < 0) f[i & 1][j + 100210] += MOD;         sf[i & 1][j + 100210] =             (sf[i & 1][j + 100209] + f[i & 1][j + 100210]) % MOD;       }       for (int j = -100000; j <= 100100; j++) {         g[i & 1][j + 100210] =             (sg[(i - 1) & 1][min(100210 + b + k * i, j + k + 100210)] -              sg[(i - 1) & 1][max(100209 + b - k * i, j - k + 100209)]) %             MOD;         if (g[i & 1][j + 100210] < 0) g[i & 1][j + 100210] += MOD;         sg[i & 1][j + 100210] =             (sg[i & 1][j + 100209] + g[i & 1][j + 100210]) % MOD;       }     }     for (int j = -100000; j <= 100100; j++) {       ans = (ans + f[t & 1][j + 100210] * sg[t & 1][j + 100209]) % MOD;     }     printf( %lld n , ans);   }   