#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    int n,x,y,f;
    ifstream in("fact.in");
    ofstream out("fact.out");
    in>>n;
    x=1;
    f=1;
    while(y<n)
    {
        f=f*f+1;
        x++;
        if(f%10==0)
        {
            y++;
        }
        if(f>=10)
        {
            f=f/10;
        }
    }
    out<<x;
    return 0;
}