#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;

ll n, s, k, dp[20001], mod = 1e9 + 7;

int main() {
  scanf("%lld%lld%lld", &n, &s, &k);
  ll sum = s - n * (n - 1) * k / 2;
  if (sum < 0) { printf("0\n"); return 0; }
  dp[0] = 1;
  for (ll i = n; i >= 1; i--) {
    for (ll j = i; j <= sum; j++) dp[j] = (dp[j] + dp[j - i]) % mod;
  }
  printf("%lld\n", dp[sum]);
}