#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cstdio>

using namespace std;

FILE *f1;
int co,cx,mo,mx;
int main()
{
	f1=fopen("bs.in","r");
	freopen("bs.out","w",stdout);
	while (fscanf(f1,"%d%d%d%d",&co,&cx,&mo,&mx)!=EOF)
	{
		if (mo>co) mo=co;if (mx>cx) mx=cx;
		int ans=0;
		if (mo<=0) ans=mx;
		else if (mx<=0) ans=mo;
		else
		{
			if (co<cx) ans=co+min(cx,mx*(co+1));
			else if (cx<co) ans=cx+min(co,mo*(cx+1));
			else ans=co+cx;
		}
		printf("%d\n",ans);
	}
	return 0;
}