N, S, K = map(int, input().split())
S -= K*N*(N-1)//2
if S<0:
    exit(print(0))
if S == 0:
    exit(print(1))

mod = 10**9+7
dp = [[0]*(S+1) for _ in range(N+1)]
dp[0][0] = 1
for i in range(1, N+1):
    for j in range(S+1):
        if j-i>=0:
            dp[i][j] = dp[i-1][j]+dp[i][j-i]
            dp[i][j] %= mod
        else:
            dp[i][j] = dp[i-1][j]
print(dp[-1][-1])