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



int main(){
	int N,S,K;
	cin >> N >> S >> K;
	S -= K*N*(N-1)/2;
	if( S < 0 ) cout << 0 << endl;
	else{	
		register int dp[2][20001];
		dp[0][S] = 1;
		register int cur = 0;
		for(register int x = N ; x >= 1 ; x--){
			for(register int j = 0 ; j <= S ; j++) dp[cur^1][j] = 0;
			for(register int s = S ; s >= 0 ; s--){
				dp[cur^1][s] += dp[cur][s];
				if( dp[cur^1][s] >= 1000000007 ) dp[cur^1][s] -= 1000000007;
				if( s - x >= 0 ){
					dp[cur][s-x] += dp[cur][s];
					if( dp[cur][s-x] >= 1000000007 ) dp[cur][s-x] -= 1000000007;
				}
			}
			cur ^= 1;
		}
		cout << dp[cur][0] << endl;
	}
	
}