#include <stdio.h>

int main() {
    int quantityX, priceX;
    int quantityY, priceY;
    int quantityZ, pricez;
    
    
    if(scanf("%d %d", &quantityX, &priceX)!=2 ||
       scanf("%d %d", &quantityY, &priceY)!=2 ||
       scanf("%d %d", &quantityZ, &priceZ)!=2) {
           printf("Invalid input\n");
           return 1;
       }
       
       
       if(quantityX < 0 || quantityY < 0 || quantityZ < 0 || priceX < 0 || priceY < 0 || priceZ < 0) {
           printf("Invalid input\n");
       } else {
           
           int totalCost = (quantityX * priceX) + (quantityY * priceY) + (quantityZ * priceZ);
           printf("%d\n",totalCost);
       }
       
       return 0;
}