#include <fstream>
#define int long long
using namespace std;

ifstream cin("fact.in");
ofstream cout("fact.out");

int MateiSauMihaiVoicuDarDacaEmihaiVoicuEokDarDacaNuTeUitiLaSursaeaCumTeitiDeObiceiSiNuEBineLol(int nr)
{
    int m5=0;
    while(nr>0)
    {
        m5=m5+nr/5;
        nr=nr/5;
    }

    return m5;
}

signed main()
{
    int nr, l=0, r=100000000LL, m;
    cin>>nr;
    r=100000000LL;
    while(m-l>1)
    {
        m=(l+r)/2;
        if(MateiSauMihaiVoicuDarDacaEmihaiVoicuEokDarDacaNuTeUitiLaSursaeaCumTeitiDeObiceiSiNuEBineLol(m)<nr)
            l=m;
        else
        r=m;
    }

    if(MateiSauMihaiVoicuDarDacaEmihaiVoicuEokDarDacaNuTeUitiLaSursaeaCumTeitiDeObiceiSiNuEBineLol(r)==nr)
        cout<<r;
    else
        cout<<-1;
    return 0;
}