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