#include <bits/stdc++.h>
using namespace std;

const int MOD = 1e9 + 7;

int n, s, k;
int dp[20001];

int main()
{
	cin >> n >> s >> k;
	
	int S = s - k * n * (n - 1) / 2;
	if (S < 0){
		cout << 0 << endl;
		return 0;
	}
	
	dp[0] = 1;
	for (int i = 0; i < n; i++){
		int ds = n - i;
		for (int s = 0; s + ds <= S; s++){
			dp[s + ds] += dp[s];
			dp[s + ds] %= MOD;
		}
	}
	
	cout << dp[S] << endl;
}