#include <iostream>
#include <fstream>
#include <set>
#include <map>
#include <queue>
#include <vector>
#include <algorithm>
#include <cmath>
#include <chrono>

#define MOD (int64_t)(1e+9 + 7)

using namespace std;

int main(int argc, const char * argv[]) {
    
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int n, s, k; cin >> n >> s >> k;
    
    vector<vector<int64_t>> dp(n + 1, vector<int64_t>(s + 1, 0));
    
    dp[0][0] = 1;
    
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= s; j++) {
            if (j >= k * i) {
                dp[i + 1][j] += dp[i][j - k * i];
                dp[i + 1][j] %= MOD;
            }
            if (j >= i + 1) {
                dp[i + 1][j] += dp[i + 1][j - i - 1];
                dp[i + 1][j] %= MOD;
            }
        }
    }
    
    cout << dp[n][s] % MOD << endl;
    
    return 0;
}