#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;
int p = 0;
double factorial(int n)
{
    double f=1;
    for(int i = 2;i<=n;i++)
        f *=i;
    return f;
}

double cifre(double n)
{
    int nr = 0, nr2 = 0;
    while(n!=0){
        if(nr2 == p)
            break;
        if(fmod(n, 10) == 0)
            {nr++;}
        n /= 10;
        nr2++;
    }
    return nr;
}

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    int i;
    for(i = 1;; i++){
        if(cifre(factorial(i)) == p)
            break;
    }
    g<<i;
    return 0;
}