#include<stdio.h>
int main()
{
   int p1,b1,p2,b2,p3,b3 ;
   if(scanf("%d %d %d %d %d %d",&p1,&b1,&p2,&b2,&p3,&b3));
   {
       printf("Invalid input");
   }else if (p1<0 || b1<0 || p2<0 || b2<0 || p3<0 || b3<0)
   {
     printf("Invalid input");  
   }
   else
   {
       long long total=(long long)p1*b1+(long long)p2*b2+(long long)p3*b3;
       printf("%lld\n",total);
   }
   return 0;
}