#include <iostream>
#include <fstream>
using namespace std;
int i,p,s,nr,ii;
int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin>>p;
    nr=0;
    i=0;
    if(p==0)fout<<1;
    else
    while(nr!=p)
    {
        i=i+5;
        ii=i;
        while(ii%5==0)
        {
            nr++;
            ii/=5;

        }
    }
    if(p!=0)
    fout<<i;
    fout.close();
    fin.close();
}