#include<stdio.h>
int main()
{
int product1, product2, product3;
int cost1, cost2, cost3, total;
scanf("%d %d", &product1, &cost1);
scanf("%d %d", &product2, &cost2);
scanf("%d %d", &product3, &cost3);
if(product1<0 || product2<0 || product3<0 || cost1<0 || cost2<0 || cost3<0)
{
    printf("Invalid input");
}
else
{
    total = product1*cost1 + product2cost2 + product3cost3;
    printf("%d", total);
}
return 0;
}