#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    int n,x=1,z=1,m=1;
    fin>>n;
    while(n>0)
    {
        x=x*10;
        n--;
    }

    while(z%x!=0)
    {
        m++;
        z=z*m;

    }
    fout<<m;

    fin.close();
    fout.close();
    return 0;
}