#include <iostream>
#include <vector>
using namespace std;

int main() {
    const int MOD = 1000000007;
    int n, s, k;
    cin >> n >> s >> k;

    s -= k * (n - 1) * n / 2;

    if(s < 0) {
        cout << 0 << endl;
    } else {
        vector<vector<int>> dp(n+1, vector<int>(s+1, 0));
        dp[0][0] = 1;
        for(int i = 1; i < n + 1; ++i) {
            for(int j = 0; j < s + 1; ++j) {
                if(j - i >= 0) {
                    dp[i][j] = (dp[i][j-i] + dp[i-1][j]) % MOD;
                } else {
                    dp[i][j] = dp[i-1][j];
                }
            }
        }

        cout << dp[n][s] << endl;
    }
}