func_code_string: #include <bits/stdc++.h>   const int mod = 1000000007;   int k, w;   int fac[1000010];   int invfac[1000010];   inline int gcd(int a, int b, int &x, int &y) {     if (b == 0) {       x = 1;       y = 0;       return a;     }     int d = gcd(b, a % b, x, y);     int t = x;     x = y;     y = t - a / b * y;     return d;   }   inline int inv(int a) {     int x, y, d = gcd(a, -mod, x, y);     return ((long long)x * d % mod + mod) % mod;   }   inline int perm(int a, int b) {     if (b > a || b < 0) return 0;     return (long long)fac[a] * invfac[a - b] % mod;   }   inline int pow(int a, int b) {     int g = 1;     for (; b; b >>= 1) {       if (b & 1) g = (long long)g * a % mod;       a = (long long)a * a % mod;     }     return g;   }   void predo() {     fac[0] = 1;     for (int i = 1; i <= k; i++) fac[i] = (long long)fac[i - 1] * i % mod;     invfac[k] = inv(fac[k]);     for (int i = k - 1; i >= 0; i--)       invfac[i] = (long long)invfac[i + 1] * (i + 1) % mod;   }   int solve() {     int maxl = k + w, minl = w + 1;     int ans = 0;     predo();     for (int l = minl; l <= maxl; l++) {       int tmp;       if (w * 2 > l + 1) {         int sl = l - w;         int midl = 2 * w - l;         tmp = (long long)perm(k, sl) * perm(k, sl) % mod * pow(k, midl - 2) %               mod *               ((long long)k * k % mod - (long long)(k - sl) * (k - sl) % mod +                mod) %               mod;       } else if (w * 2 == l + 1) {         int sl = w - 1;         int midl = 1;         tmp = (long long)k *               ((long long)perm(k, sl) * perm(k, sl) % mod -                (long long)perm(k - 1, sl) * perm(k - 1, sl) % mod + mod) %               mod;       } else {         int sl = w;         int midl = l - 2 * w;         int k2 = k - midl;         tmp =             ((long long)perm(k, midl) * perm(k2, sl) % mod * perm(k2, sl) % mod -              (long long)perm(k, midl + 2) * perm(k2 - 2, sl - 1) % mod *                  perm(k2 - 2, sl - 1) % mod +              mod) %             mod;       }       ans = (ans + tmp) % mod;     }     return ans;   }   int main() {     scanf( %d %d n , &k, &w);     printf( %d n , solve());     return 0;   }   