#include <stdio.h>

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