#include <fstream>

using namespace std;

int main()
{
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    long long p;
    cin>>p;
    if(p==0)
    {
        cout<<"1"<<endl;
    }
    else
    {
        long long st=1,dr=p,mij,nr,ok=0;
        while(dr>=st)
        {
            int mij=(st+dr)/2;
            nr=1LL*mij*5;
            long long put5=5,cnt=0;
            while(put5<=nr)
            {
                cnt+=nr/put5;
                put5*=5;
            }
            if(cnt==p)
            {
                cout<<nr<<'\n';
                ok=1;
                break;
            }
            if(cnt<p)
            {
                st=mij+1;
            }
            else
            {
                dr=mij-1;
            }
        }
        if(ok==0)
        {
            cout<<"-1"<<endl;
        }
    }
    return 0;
}