#include<bits/stdc++.h>
#define mod 1000000007
using namespace std;

int main()
{
    int N,S,K;scanf("%d %d %d",&N,&S,&K);
    int minus=0;
    for(int i=1;i<N;i++)minus+=i*K;
    int s=S-minus;
    if(s<0){printf("0");return 0;}
    vector<vector<int>> dp(N+1,vector<int>(s+1,0));
    dp[0][0]=1;
    for(int i=1;i<N+1;i++)for(int j=0;j<s+1;j++)
    {
        if(j-i>-1)dp[i][j]=(dp[i-1][j]+dp[i][j-i])%mod;
        else dp[i][j]=dp[i-1][j];
    }
    printf("%d\n",dp[N][s]);
}