#include <iostream>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <cmath>
#include <cstdarg>
#include <cstdlib>
#include <string>

#include <vector>
#include <tuple>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;

int main(int argc, char const *argv[]) {
    int N, S, K;
    int div = 1000000007;
    cin >> N >> S >> K;
    S -= N * (N - 1) / 2 * K;
    if (S < 0) {
        cout << 0 << endl;
        return 0;
    } else if (S == 0) {
        cout << 1 << endl;
        return 0;
    }
    int dp[N + 1][S + 1];
    memset(dp[0], 0, sizeof(dp[0]));
    dp[0][0] = 1;
    for (int i = 1; i <= N; i ++) {
        for (int j = 0; j <= S; j ++) {
            if (j < i) {
                dp[i][j] = dp[i-1][j];
            } else {
                dp[i][j] = (dp[i-1][j] + dp[i][j-i]) % div;
            }
        }
    }
    cout << dp[N][S] << endl;
    return 0;
}