#include<iostream>
#include<cstdlib>
using namespace std;
int cmp(const void *p, const void *q)
 {

    return *(int *)p-*(int *)q;
 }
int main()
{
    int a[5];
    cin>>a[1]>>a[2]>>a[3]>>a[4];
    int p=a[1]*a[2]*a[3]*a[4];
    int smax=-1,t;
    qsort(a+1,4,sizeof(int),cmp);
    cout<<a[1]*a[2]+a[3]*a[4];
    return 0;
}