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

int N,S,K;
vector<int> v;


int main(){
	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 = 0 ; s <= S ; s++){
				if( dp[cur][s] == 0 ) continue;
				for(register int k = 0 ; k <= s/x ; k++){
					dp[cur^1][s-k*x] += dp[cur][s];
					if( dp[cur^1][s-k*x] >= 1000000007 ) dp[cur^1][s-k*x] -= 1000000007;
				}
			}
			cur ^= 1;
		}
		cout << dp[cur][0] << endl;
	}
	
}