#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;

const int MOD = 1e9+7;

typedef long long ll;

int main(){
  int n, s, k; cin >> n >> s >> k;

  ll dp[n+1][s+1]; //dp[i][j]:i人でjを分ける総数
  memset(dp, 0, sizeof(dp));
  dp[1][0] = 1;

  for(int i=1; i<=n; i++){
    for(int j=0; j<=s; j++){
      int rem = n-i+1;
      if(j >= k*rem ){
        dp[i][j] += dp[i-1][j-k*rem];
      }
      if(j >= rem) {
        dp[i][j] += dp[i][j-rem];
      }
      dp[i][j] %= MOD;
    }
  }

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

  return 0;
}