import sys
def MI(): return map(int,sys.stdin.readline().rstrip().split())


N,M,D1,D2 = MI()
mod = 10**9+7

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

fac = [0]*(N+M)
fac[0] = 1
for i in range(1,N+M):
    fac[i] = (i*fac[i-1]) % mod
fac_inv = [0]*(N+M)
a = pow(fac[-1],mod-2,mod)
for i in range(N+M-1,-1,-1):
    fac_inv[i] = a
    a *= i
    a %= mod


def nCr(n,r):
    if n < r:
        return 0
    return (fac[n]*fac_inv[r]*fac_inv[n-r]) % mod


ans = 0
for i in range(N):
    X = MM-i*(D+1)
    a = nCr(N-1,i)*nCr(X+N,N)
    a %= mod
    if i % 2 == 0:
        ans += a
    else:
        ans -= a
    ans %= mod

print(ans)