#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int s,d,m,p,n,x;
int main()
{
    f>>p;
    if(p==0) g<<1;
    else
    {
    s=1;d=800000000;
    while(s<=d && n!=p)
    {
    n=0;
    m=(s+d)/2;
    x=m/5;
    while(x){
    n+=x;x/=5;}
    if(n>p) d=m-1;
    else s=m+1;
    }}
    g<<m-m%5;
    return 0;
}