#include<stdio.h>
int main()
{
  int quantity X, price X;
  int quantity Y, price Y;
  int quantity Z, price Z;
  int totalcost=0;
  if(scanf("%d %d",&quantity X,&price X)!=2||quantity X<0||price X<0)
  {
      printf("Invalid input");
  }
  else if(scanf("%d %d",&quantity Y,&price Y)!=2||quantity Y<0||price Y<0)
  {
      printf("Invalid input");
  }
  else if(scanf("%d %d",&quantity Z,&price Z)!=2||quantity Z<0||price Z<0)
  {
      printf("Invalid input");
  }
  totalcost=(quantity X*price X)+(quantity Y*price Y)+(quantity Z*price Z);
  {
      printf("%d",totalcost);
  }
    
}