#include <fstream>
using namespace std;
int main()
{
    int p,k,n,i,x;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    k=0;n=0;
    if(p==0)
        g<<1;
    else
    {
        while(k<=p)
    {
        n=n+5;
        x=n;
        i=0;
        while(x%5==0)
        {
            x=x/5;
            i=i+1;
        }
        k=k+i;
    }
    g<<n-5;
    }
    f.close();
    g.close();
    return 0;
}