#include<fstream>
using namespace std;
int main()
{
    int n,p,f,ls=5,ld=400000015,g=0,x;
    ifstream t("fact.in");ofstream r("fact.out");
    t>>p;
    if(p==0)r<<"1";
    else
    while(ls<=ld && g==0)
    {
    n=(ls+ld)/2;
    x=0;
    f=5;
        while(f<=n)
        {
            x+=n/f;
            f*=5;
        }
    if(x==p){r<<n/5*5;g=1;}
    else if(x<p)ls=n+1;
    else ld=n-1;
    }
    return 0;
}