#include <iostream>
#include <fstream>
using namespace std;
long long int p,r,numar,mijloc,inceput,sfarsit;
int main()
{
    ifstream ka("fact.in");
    ofstream ki("fact.out");
    ka>>p;
    if(p==0)
    ki<<"1";
    else
    {
    sfarsit=1000000000;
    inceput=1;
    while(inceput<sfarsit)
    {
        numar=0;
        if(inceput==sfarsit-1)
        {
            mijloc=inceput;
            r=5;
            while(mijloc/r>=1)
            {
                numar+=mijloc/r;
                r*=5;
            }
            if(numar==p)
            {ki<<mijloc-mijloc%5;
            break;}
            else
            {
                mijloc=sfarsit;
            r=5;
            while(mijloc/r>=1)
            {
                numar+=mijloc/r;
                r*=5;
            }
            if(numar!=p)
            {ki<<"-1";
            break;}
            }
        }
    mijloc=inceput+(sfarsit-inceput)/2;
    r=5;
    while(mijloc/r>=1)
    {
        numar+=mijloc/r;
        r*=5;
    }
    if(numar==p)
    {ki<<mijloc-mijloc%5;
    break;}
    else if(numar<p)
    inceput=mijloc;
    else if(numar>p)
    sfarsit=mijloc;
    }
    }

}