#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

int main()
{
    long long nrzero,cinci=0,doi=0,numar=0,valrez=0;
    fin>>nrzero;
    while(nrzero!=0)
    {
        numar++;
        valrez=numar;
        while(valrez%2==0)
        {
            valrez=valrez/2;
            doi++;
        }
        while(valrez%5==0)
        {
            valrez=valrez/5;
            cinci++;
        }
        if(cinci!=0 && doi!=0)
        {
            cinci--;
            doi--;
            nrzero--;
        }
    }
    if(numar!=0)
        cout<<numar;
    else
        cout<<1;
    fin.close();
    fout.close();
    return 0;
}