#include <iostream>
#include<fstream>
using namespace std;

int main()
{

    int n, i, j, k, v[100], u[100], cnt=0, max=0, maxi=0, min=1000, mini=1000, n1, n2;


    for(i=1;i<=4;i++)
    {
        cin>>v[i];
    }


    for(i=1;i<=4;i++)
    {
        if(v[i]>max) max=v[i];
    }

    n1=max;

    for(i=1;i<=4;i++)
    {
        if((v[i]>maxi)&&(v[i]<max)) maxi=v[i];


    }


    n1=n1*maxi;

    for(i=1;i<=4;i++)
    {
        if(v[i]<min)min=v[i];

    }

    n2=min;

    for(i=1;i<=4;i++)
    {
        if((v[i]!=min)&&(v[i]!=max)&&(v[i]!=maxi))mini=v[i];
    }

    n2=n2*mini;
    n=n1+n2;
    cout<<n;


    return 0;
}