#include <stdio.h>
int main()
{
    int quantityX,priceX;
    int quantityY,priceY;
    int quantityZ,priceZ;
    scanf("%d %d",&qyantityX, &princeX);
    scanf("%d %d",&qyantityY, &princeY);
    scanf("%d %d",&qyantityZ, &princeZ);
    if (qyantityX <0 || priceX <0 || quantityY <0 || priceY <0 || quantityZ <0 || princeZ <0)
    {
        printf("invalid input");
    }
    else
    {
        int total_cost = quantityX*pricex+quantityY*priceY+quantityZ*priceZ;
        printf("%d",total_cost);
    }
    return 0;
}