#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int n;
int Rezolvare(int x)
{
    int s=0,y=5;
    while(y<=x)
    {
        s=s+x/y;
        y=y*5;
    }
    return s;
}
int CautBin(int y)
{
    int st=1,dr=2073741824,m,poz=0;
    while(st<=dr)
    {
        m=(st+dr)/2;
        if(Rezolvare(m)==y)
            poz=m;
        if(Rezolvare(m)<y)
            st=m+1;
        else if(Rezolvare(m)>=y)
            dr=m-1;
    }
    return poz;
}
int main()
{
    fin>>n;
    if(CautBin(n)==0)
        fout<<"-1"<<"\n";
    else
    fout<<CautBin(n)<<"\n";
}