#include<fstream>
#define numaru (1<<31-1)
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;
    long long k,q,w,e;
    f>>p;
    if(p==0) k=1;
    else
    {
        q=5; w=numaru;
        while(true)
        {
            k=(q+w)>>1;
            e=verif(k);
            if(e==p) break;
            else if(e<p) q=k;
            else w=k;
        }
    }
    g<<k/5*5<<"\n";
    f.close();
    g.close();
    return 0;
}