找到最小的数满足里面有n个不被x整除的整数，m个不被y整除的数，且这n个数和m个数完全不重合。x和y都是质数

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int n, m,a,b;
//int a[N];
bool check(int x){
	int n1=x/a;
	int m1=x/b;
	int c=x/(a*b);
	int p=n1-c,q=m1-c;
	int lf=x-n1-m1+c;
	int p1=max(m-p,0LL);
	int q1=max(n-q,0LL);
	if(p1+q1<=lf)return true;
	return false;
}
void solve(){
	cin>>n>>m>>a>>b;
	int l=0,r=2e9;
	while(l<r){
		int mid=(l+r)>>1;
		if(check(mid))r=mid;
		else l=mid+1;
	}
	cout<<l<<endl;
}