#include<fstream>
#define sarpe_muscat true
using namespace std;
int verif(long long n)
{
    int s=0,o=1;
    while(o<=n)
        s+=(n/(o*=5));
    return s;
}
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    int p,k,q;
    f>>p;
    if(p==0) k=1;
    else
    {
        k=5*p;
        do
        {
            q=verif(k);
            if(q==p) break;
            else if(q>p) k-=5;
            else k+=5;
        } while( sarpe_muscat );
        g<<k<<"\n";
    }
    f.close();
    g.close();
    return 0;
}