import sys
def MI(): return map(int,sys.stdin.readline().rstrip().split())


N,S,K = MI()
mod = 10**9+7

S -= K*(N*(N-1)//2)
if S < 0:
    print(0)
else:
    dp = [[0]*(S+1) for _ in range(N+1)]  # dp[i][j] = jをi個に分割する方法
    dp[0][0] = 1
    for i in range(1,N+1):
        for j in range(S+1):
            dp[i][j] = dp[i-1][j]
            if j >= i:
                dp[i][j] += dp[i][j-i]
            dp[i][j] %= mod
    print(dp[N][S])