#include <fstream>

#define I_F "bs.in"
#define O_F "bs.out"

using namespace std;

long max(long a, long b);
long min(long a, long b);
void Exchange(long &a, long &b);

int main()
{
	long co,cx,mo,mx;
	long ans;
	
	ifstream fin(I_F);
	ofstream fout(O_F);
	while (!fin.eof())
	{
		ans=0;
		fin>>co>>cx>>mo>>mx;
		if ((mo==0)||(mx==0))
			ans=max(min(co,mo),min(cx,mx));
		else
		{
			if (co>cx)
			{
				Exchange(co,cx);
				Exchange(mo,mx);
			}
			ans=co+min(min(cx/(co+1),mx)*(co+1),cx);
		}
		fout<<ans<<'\n';
	}
	fin.close();
	fout.close();
	return 0;
}

long max(long a, long b)
{
	if (a>b)
		return a;
	else
		return b;
}

long min(long a, long b)
{
	if (a<b)
		return a;
	else
		return b;
}

void Exchange(long &a, long &b)
{
	long t=a;
	a=b;
	b=t;
}