#include<stdio.h>
int main(){
    int qtyX,priceX;
    int qtyY,priceY;
    int qtyZ,priceZ;
    if(scanf("%d %d",&qtyX, &priceX) !=2) ||scanf("%d %d",&qtyY,priceY)!=2 || scanf("%d %d",&qtyZ, &priceZ) !=2)
    {
        printf("Invalid input");
    return 0;
        
    }
    if (qtyX <0 || priceX <0 ||qtyY <0 ||priceY <0 || qtyZ <0 ||priceZ <0){
        printf("Invalid input");
        return 0;
    }
    long total=(qtyX * priceX) +(qtyY * priceY)+(qtyZ * priceZ);
    printf("%ld",total);
    return 0;
}