#include<iostream>
 
using namespace std;
 
int main()
 
{
 
 int a[10] = { 10,9,8,7,6,5,4,3,2,1 },left=0,right=9,n;
 
 cin >> n;
 
 while (left <= right)
 
 {
 
 int middle = left + (right - left) / 2;
 
 if (a[middle] < n)
 
 right = middle - 1;
 
 else if (a[middle] > n)
 
 left = middle + 1;
 
 else
 
 {
 
 cout << middle ;
 
 break;
 
 }
 
 }
 
 if (n < 1 || n>10)
 
 cout << -1;
 
 return 0;
 
 
 
}