#include<stdio.h>
int main()
{
    int V,v;
    int H,h;
    int K,k;
    scanf("%d %d",&V,&v);
    scanf("%d %d",&H,&h);
    scanf("%d %d",&K,&k);
    if(V<0 || v<0 || H<0 || h<0 || K<0 || k<0)
    printf("Invalid input");
    else
    printf("%d",V*v+H*h+Z*z);
    return 0;
}