a, b, n, m = map(int, input().split())
Flag = True

while Flag:
    if a < b:
        ans = a
        a += 1
        b -= m
        
        if a >= b:
            Flag = False
            if b > ans:
                print(ans)
            else:
                print(b)
    
    else:
        ans = b
        a -= n
        b += 1
        
        if a <= b:
            Flag = False
            if a < ans:
                print(a)
            else:
                print(ans)