N, M, P, Q = map(int, input().split())

def mod_div(a, b, p):
    return (a * pow(b, p - 2, p)) % p

ans = []
for _ in range(Q):
    x, f = map(int, input().split())
    y = mod_div(f, x, P)
    if y == 0:
        y = P
    ok = -1
    ng = M
    while ng - ok > 1:
        mid = (ok + ng) // 2
        if P * mid + y <= M:
            ok = mid
        else:
            ng = mid
    ans.append(ok + 1)

print(*ans, sep="\n")