P, Q, x, y = map(int, input().split())
def solve():
    f = x + (10 ** 9999 + P - 1) // P * P
    sf = str(f)
    k = len(sf)
    g = P
    rf = 0
    rg = 0
    for ff in sf[::-1]:
        rf = (rf * 10 + int(ff)) % Q
        rg = (rg * 10 + g) % Q
        g //= 10
    t = (y - rf) * pow(rg, Q - 2, Q) % Q
    n = f + t * P
    return n

print(solve())