/*#include<iostream>
#include<fstream>
using namespace std;
int main()
{
    long long n=5,nr,p,aux;
    fstream f("fact.in");
    ofstream g("fact.out");
    while(f>>p)
    {
        if(p==0)
            g<<1<<endl;
        if(p<0)
            g<<-1<<endl;
        n=0;
        while(p>0)
        {
            nr=0;
            n+=5;
            aux=n;
            while(aux%5==0)
            {
                aux/=5;
                nr++;
            }
            p-=nr;
        }
        if(n>0)
           {
               aux=n;
               if(p<0)
                  aux=-1;
               g<<aux<<endl;}

   }
    return 0;
}
*/
#include <iostream>
#include <fstream>
#define NMax 100000001
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int fct (int x)
{
    int a=5,rez=0;
    while (x/a)
    {
        rez=rez+x/a;
        a=a*5;
    }
    return rez;
}
int main ()
{
    int p,val;
    f>>p;
    if (p==0) g<<1;
    else
    {
        int min=1,max=NMax,mid;
        bool ok=false;
        while (min<max && !ok)
        {
            mid=(min+max)/2;
            val=fct(mid);
            if (val<p) min=mid+1;
            else if (val>p) max=mid-1;
            else ok=true;
        }
        if (ok)
        {
            while (mid%5) mid--;
            g<<mid;
        }
        else g<<-1;
    }
}