mod = 10**9+7
N, S, K = map(int, input().split())

for n in range(N):
    S -= n*K

P = dict()
for n in range(S+1):
    for k in range(1, N+1):
        if n==0 or k==1:
            P[(n, k)] = 1
        elif n<k: 
            P[(n, k)] = P[(n, n)]
        else:
            P[(n, k)] = P[(n, k-1)]+P[(n-k, k)]
        P[(n, k)] %= mod

print(0 if S<0 else P[(S, N)])