MOD = 1000000007
N,S,K = map(int,input().split())
D = S-(N-1)*N//2*K

if D >= 0:

    dp = [[0 for j in range(D+1)] for i in range(N+1)]
    dp[0][0] = 1
    
    for i in range(1,N+1): #分割数
        for j in range(D+1):
            dp[i][j] = dp[i-1][j]
            if j-i >= 0:
                dp[i][j] += dp[i][j-i]
            dp[i][j] %= MOD
    
    print(dp[N][D])
    
else:
    print(0)