def main():
    n,s,k=map(int,input().split())
    s=s-(k*n*(n-1))//2
    M=10**9+7
    if s<0:
        print(0)
    else:
        dp=[[1]*n for _ in [0]*(s+1)]
        for i in range(1,s+1):
            for j in range(n):
                if j==0:
                    dp[i][j]=dp[i-1][j]
                elif i-j-1<0:
                    dp[i][j]=dp[i][j-1]
                else:
                    dp[i][j]=(dp[i][j-1]+dp[i-j-1][j])%M        
        print(dp[s][n-1])
    
if __name__ == '__main__':
	main()