#include<stdio.h>
int main()
{
  int x, price 1;
  int y, price 2;
  int z, price 3;
  int totalcost=0;
  if(scanf("%d%d",&x,&price 1)!=2||x<0||price<0)
  {
      printf("Invalid input");
  }
  else if(scanf("%d%d",&y,&price 2)!=2||y<0||price y<0)
  {
      printf("Invalid input");
  }
  else if(scanf("%d%d",&z,&price 3)!=2||z<0||price z<0)
  {
      printf("Invalid input");
  }
  totalcost=(x*price 1)+(y*price 2)+(z*price 3);
  {
      printf("%d",totalcost);
  }
    
}