#include <bits/stdc++.h>
using namespace std;
int calculare(int nr)
{
    int countq=0;
    int putere=5;
    while(putere<=countq)
    {
        countq=countq+nr/putere;
       putere=putere*5;
    }
    return countq;
}
int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    long long st,dr,mij;
    int p,u;
    fin>>p;
    if(p==0)
    {
        fout<<1;
        return 0;
    }
    st=1;
    dr=p*5;
    while(st<=dr)
    {
        mij=(st+dr)/2;
        if(calculare(mij)<p) st=mij+1;
        else
            st=mij-1;
        if(calculare(mij)==p)
                int u=1;
    }
    if(u) fout<<st;
    else
        fout<<-1;
    cout<<'\n';
    return 0;
}