#include<stdio.h>

int main()
{
  int l,lcopy,carry=0,ans[20]={0},i;

  scanf("%d",&l);

  l--;
  lcopy=l;

  for (i=0;l>0;i++) {
    ans[i]=l%10;
    l/=10;
  }

  i--;

  for (;i>=1;i--) {
    ans[i-1]+=(ans[i]%4)*10;
    ans[i]/=4;
  }
  ans[0]/=4;

  l=lcopy;

  for (i=0;i<20;i++) {
    ans[i]*=l;
    ans[i]+=carry;
    carry=ans[i]/10;
    ans[i]%=10;
  }

  i=19;
  while (ans[i]==0) {
    i--;
  }

  for (;i>=0;i--) {
    printf("%d",ans[i]);
  }
  return 0;
}