#include<stdio.h>
int main()
{
    int X,x;
    int Y,y;
    int Z,z;
    scanf("%d %d",&X,x);
    scanf("%d %d",&Y,y);
    scanf("%d %d",&Z,z);
    if(X<0 || x<0 || Y<0 || y<0 ||Z<0 || z<0)
    printf("Invalid input");
    else
    printf("%d",X*x+Y*y+Z*z);
    return 0;
}