#include<stdio.h>
int main(){
    int quantityX,quantityY,quantityZ;
    float priceX,priceY,priceZ,totalCost;
    scanf("%d %f",&quantityX,&priceX);
    scanf("%d %f",&quantityY,&priceY);
    scanf("%d %f",&quantityZ,&priceZ);
    if(quantityX<0 || quantityY<0 || quantityZ<0 || priceX<0 || priceY<0 || priceZ<0){
        printf("Invalid input\n");
    }else{
        totalcost=(quantityX*priceX)+(quantityY*priceY)+(quantityZ*priceZ);
        printf("%.0f\n",totalcost);
    }
}