#include <fstream>

using namespace std;

ifstream cin("fact.in");
ofstream cout("fact.out");

int p;

int nrde0( int n)
{
    int putere5=5, numar=0;
    while(putere5<=n)
    {
        numar+=n/putere5;
        putere5*=5;
    }
    return numar;
}

int cb(int p)
{
    int st=1,dr=p;
    while(st<=dr)
    {
        int mij= (st+dr)/2;
        int mij0=nrde0(5*mij);
        if(p==mij0)
        {
            return 5*mij;
        }
        else if(p>mij0)
        {
            st=mij+1;

        }
        else
        {
            dr=mij-1;
        }

    }
    return -1;
}


int main()
{
    cin>>p;
    if(p==0)
        cout<< 1 << '\n';
    else
        cout<< cb(p);
    return 0;
}