#include<bits/stdc++.h>
using namespace std;
int main(){
    long long n,s,k,i,j;cin >> n >> s >> k;
    s -= n*(n-1)/2*k;
    if(s<0){
        cout << 0 << "\n";return 0;
    }
    long long dp[s+1][n+1] = {};dp[0][0] = 1;//dp[i][j] はiをj分割
    for(i=0;i<=s;i++){
        for(j=1;j<=n;j++){
            if(i>=j) dp[i][j] = (dp[i][j-1]+dp[i-j][j])%1000000007;
            else dp[i][j] = dp[i][j-1];
        }
    }
    cout << dp[s][n] << "\n";
}