#include <bits/stdc++.h>

using namespace std;


ifstream fin("fact.in");
ofstream fout("fact.out");

int main()
{
    int p,i;

    long long st,dr,mij,nrzero;

    fin>>p;

    st=1;dr=5*p;

    while(st<=dr)
    {
        mij=(dr+st)/2;
        nrzero=0;
        for(i=5;i<=mij;i=i*5)
            nrzero=nrzero+mij/i;

        if(nrzero==p)
            break;


        else if(nrzero<p) st=mij+1;
        else if(nrzero>p) dr=mij-1;
    }



    if(p==0) fout<<1;
    else if(st<=dr) fout<<mij-mij%5;
    else fout<<-1;

    return 0;
}