#include<stdio.h>
int main()
{
    int qx,px,qy,py,qz,pz;
    long total;
    if (scanf("%d %d", &qx, &px) !=2 || scanf("%D %d", &qy, &py) !=2 || scanf("%d %d",&qz,&pz) !=2)
    {
        printf("Invalid input\n");
        return 0;
    
    }
    if (qx<0 || qz<0 || qy<0 || px=0 || py<0 || pz<0)
    {
        printf("Invalid input\n");
        return 0;
    }
    total=(long)qx*px+(long)qy*py(long)qz*pz;
    printf("%d\n", total);
    return 0;
}