#inculde<stdio.h>
int main()
{
    int quantity x,pricex,quantity y,price y,quantity z,price z;
    int totalcost;
    scanf("%d %d",&quantityx, &pricex);
    scanf("%d %d",&quantityy, &pricey);
    scanf("%d %d",&quantityz, &pricez);
    totalcost=((quantity x*price x)+(quantity y*price y)+(quantity z*price z));
    if((quantity x<0||quantity y<0||quantity z<0)||(price x<0||price y<0||price z<0))
    printf("Invalid input");
    else
    printf("%d",totalcost);
    return 0;
    
}