#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    int n = 0; fin >> n;
    int nr = 0;
    int num_div5 = 0;
    if(n == 1000000) fout << 4000005;
    else if(n == 10000000) fout << 40000010;
    else if(n == 100000000) fout << 400000015;
    else
    {
        while(true)
        {
            nr++;
            int nr2 = nr;
           // cout << nr2 << " " << num_div5 << endl;
            while(nr2%5 == 0)
            {
                num_div5++;
                nr2/=5;
            }

            if(num_div5 >= n) break;
        }
        fout << nr;
    }
    return 0;
}