#include<stdio.h>
int main()
{
     int x_qty, x_price, y_qty, y_price, z_qty, z_price;
    if(scanf("%d %d",&x_qty,&x_price)!=2||
    scanf("%d %d",&y_qty,&z_price)!=2||
    scanf("%d %d",&z_qty,&z_price)!=2||
        x_qty<0||x_price<0||
        y_qty<0||y_price<0||
        z_qty<0||z_price<0)
    {
        printf("Invalid input");
        return 0;
    }
    int total_cost=x_qty*x_price+y_qty*y_price+z_qty*z_price;
    printf("%d",total_cost);
    return 0;