N, M, D1, D2 = map(int, input().split())
mod = 10**9 + 7

D = D2 - D1
x = (M - 1) - D1*(N - 1)

fac = [1 for _ in range(N+x+1)]
for i in range(N+x):
    fac[i+1] = (i+1)*fac[i]%mod

print(sum([(-1)**j * fac[x+N-j*(D+1)] * pow(N*fac[x-j*(D+1)]*fac[j]*fac[N-j-1], mod - 2, mod)\
           for j in range(min(N, 1+x//(D+1)))])%mod)