import sys
readline = sys.stdin.readline

N, M, d1, d2 = map(int, input().split())
mod = 10**9 + 7

max_n = 2 * 10**6
fac, inv = [1]*(max_n+1), [0]*(max_n+1)
for i in range(2, max_n+1):
    fac[i] = fac[i-1] * i % mod
inv[-1] = pow(fac[-1], mod-2, mod)
for i in range(max_n, 0, -1):
    inv[i-1] = inv[i] * i % mod

d = d2 - d1
x = M - 1 - d1 * (N-1)
if x < 0:
    print(0)
    exit()

ans = 0

for i in range(N):
    sign = -1 if i & 1 else 1
    if x+N-(d+1)*i >= N:
        ans += fac[x+N-(d+1)*i] * inv[N] * inv[x-(d+1)*i]\
            * fac[N-1] * inv[i] * inv[N-1-i] * sign % mod

print(ans % mod)