#include<iostream>
using namespace std;
int maxim,maxim2,minim,minim2,lit,a,b,c,d;
int main()
{
	maxim=-1;
	maxim2=-1;
	lit=0;
	
	cin>>a>>b>>c>>d;
	
	if(a>maxim) maxim=a,lit=1;
	if(b>maxim) maxim=b,lit=2;
	if(c>maxim) maxim=c,lit=3;
	if(d>maxim) maxim=d,lit=4;

	if(a>maxim2&&lit!=1) maxim2=a;
	if(b>maxim2&&lit!=2) maxim2=b;
	if(c>maxim2&&lit!=3) maxim2=c;
	if(d>maxim2&&lit!=4) maxim2=d;

	lit=0;
	minim=1000;
	minim2=1000;
	
	if(a<minim) minim=a,lit=1;
	if(b<minim) minim=b,lit=2;
	if(c<minim) minim=c,lit=3;
	if(d<minim) minim=d,lit=4;

	if(a<minim2&&lit!=1) minim2=a;
	if(b<minim2&&lit!=2) minim2=b;
	if(c<minim2&&lit!=3) minim2=c;
	if(d<minim2&&lit!=4) minim2=d;
	
	cout<<maxim*maxim2+minim2*minim;
	
	return 0;
}