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

if S==0:
    print(1)
    exit()
if S < 0:
    print(0)
    exit()

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):
        dp[i][j] = dp[i-1][j]
        if j-i >= 0:
            dp[i][j] += dp[i][j-i]

print(dp[-1][-1]%(10**9+7))