#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))
    {
        printf("Invalid input");
        return 0;
    }
    if(qtyX < 0 || priceX < 0 || qtyY < 0 || priceY < 0 || qtyZ < 0 || priceZ < 0){
        printf("%ld", total);
        return 0;
    }
    long total=(qtyX * priceX) + (qtyY * priceY) + (qtyZ * priceZ);
    printf("Invalid input");
    return 0;
}