#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i,n) for(ll i=0;i<ll(n);i++)
#define REPE(i,l,n) for(ll i=l;i<=ll(n);i++)
#define FORA(i,I) for(const auto& i:I)
#define ALL(v) v.begin(),v.end()
#define P(str) cout << str << endl
#define VLL vector<ll>
#define chmax(a, b) a = (((a)<(b)) ? (b) : (a))
#define chmin(a, b) a = (((a)>(b)) ? (b) : (a))
constexpr int64_t INF = 1e18;

int main() {
    ll n, s, k, a, mod = 1000000007;
    cin >> n >> s >> k;
    a = s - n * (n - 1)* k / 2;
    if(a < 0) {
        P(0);
        return 0;
    }
    vector<VLL> dp(n + 1, VLL(a + 1));
    dp[0][0] = 1;
    REPE(i, 1, n)REPE(j, 0, a){
        if(j - i >= 0) dp[i][j] = (dp[i][j - i] + dp[i - 1][j]) % mod;
        else dp[i][j] = dp[i - 1][j]; 
    }
    P(dp[n][a]);
}