#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
int main(){
   int n,s,k;
   cin >> n >> s >> k;
   s -= k * n * (n - 1) / 2;
   if (s < 0){
      cout << 0 << endl;
   } else {
      vector<vector<int>> dp(n + 1, vector<int>(s + 1));
      dp[0][0] = 1;
      for (int i = 1; i <= n; i++){
         for (int j = 0; j <= s; j++){
            if (j - i >= 0) dp[i][j] = (dp[i - 1][j] + dp[i][j - i]) % MOD;
            else dp[i][j] = dp[i - 1][j] % MOD;
         }
      }
      cout << dp[n][s] << endl;
   }
}