#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
#define int ll
typedef pair<int,int> pii;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a) (a).begin(),(a).end()
#define pb emplace_back

const ll MOD = 1e9+7;
signed main(){
    int n,s,k;
    cin>>n>>s>>k;
    s -= n*(n-1)/2*k;
    
    static int dp[301][20001];
    rep(i,301)rep(j,20001)dp[i][j] = 0;
    dp[0][0] = 1;
    
    for(int i=1;i<=n;i++){
        for(int j=0;j<=s;j++){
            int pay = 0;
            int remain = n-i+1;
            while(1){
                if(j-pay>=0){
                    dp[i][j] += dp[i-1][j-pay];
                    if(dp[i][j]>MOD)dp[i][j]-=MOD;
                }
                else break;
                pay += remain;
            }
        }
    }
    cout<<dp[n][s]<<endl;
}