import sys, itertools
 
sys.setrecursionlimit(500005)
stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().strip()

a, b, n, m = na()

Flag = True
ans = 9999999999999999999

while Flag:
    if a < b:
        ans = a
        a += 1
        b -= m
        
        if not(a < b):
            Flag = False

    elif a > b:
        ans = b
        a -= n
        b += 1

        if not(a > b):
            Flag = False

    else:
        Flag = False

print(max(min(a, b), ans))