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