#include<cstdio>
#include<stdlib.h>
#include<algorithm>
#include<fstream>
#include<iostream>
using namespace std;
int main()
{

    FILE* si=fopen("factorial.in","r");
    ofstream so;
    so.open("factorial.out");
    int p;
    fscanf(si,"%i",&p);
    int i,n,cont=0;
    for(n=1;;++n)
    {
        i=n;
        while(i%5==0)
        {
            ++cont;
            i=i/5;
        }
        if(cont>=p)
        {
            so<<n;
            break;
        }
    }

}