#include <iostream>
#include <vector>
using namespace std;
using ll = long long int;
constexpr ll MOD = 1'000'000'007;

int main(){
    int n, s, k;
    cin >> n >> s >> k;
    vector<vector<ll>> dp(n+1, vector<ll>(s+10, 0));
    dp[0][0] = 1;
    for(int i = 1; i <= n; i++){
        for(int j = 0; j < s+10; 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];
            }
        }
    }

    if(s-k*n*(n-1)/2 >= 0) cout << dp[n][s-k*n*(n-1)/2] << endl;
    else cout << 0 << endl;
    return 0;
}