这里v是所选1到v这个序列的最大值，然后要求最小值，就要想到最大值最小化，就要用二分搜素
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
int main()
{
ll cnt1,cnt2,x,y,xb,yb,xyb,low,up,mid,ans=inf;
scanf("%lld %lld %lld %lld",&cnt1,&cnt2,&x,&y);
low=0;
up=1e15;
while(low<=up)
{
mid=(low+up)>>1;
//cout<<"******************************88"<<endl;
//cout<<"mid:"<<mid<<" low:"<<low<<" up:"<<up<<endl;
//cout<<"******************************88"<<endl;
xb=mid/x;
yb=mid/y;
xyb=mid/(x*y);
if((mid-xyb>=cnt1+cnt2)&&(mid-xb>=cnt1)&&(mid-yb>=cnt2))
{
ans=mid;
up=mid-1;
}
else
low=mid+1;
}
printf("%lld
",ans);
return 0;
}