#include<fstream>
using namespace std;
int nrzero(int x)
{
    int nr=0,n5=5;
    while(n5<=x)
    {
        nr+=x/n5;
        n5*=5;
    }
    return nr;
}
int main()
{
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    int n,ans;
    cin>>n;
    int st=1,dr=100000000;
    if(n==0)
        cout<<1;
    while(st<=dr)
    {
        int mij=(st+dr)/2;
        if(nrzero(mij)<n)
            st=mij+1;
        else
        {
            dr=mij-1;
            ans=mij;
        }

    }
    if(nrzero(ans)==n)
        cout<<ans;
    else
        cout<<-1;
}