#include <fstream>
#include <cmath>
using namespace std;
ifstream cin("fact.in");
ofstream cout("fact.out");
#define mod 1e8;
int factorial(int n){
	
long long fact = 1;
    for(int i = 1; i <= n; i++) {
        fact = fact * i;
    }
    return fact;
}
int zero(int fact){
	int x;
	int cnt  = 0;
	while(fact != 0){
         x = fact%10;
         if(x == 0){
           cnt ++;
         }
		fact = fact /10;
	}
	return cnt;
}
int main(){
    int  n;
    cin >> n;
    for(int i = 0; i <= 1e7; i++){
        int x; 
        x = factorial(i);
        if(zero(x) == n){
        	cout << i << endl;
        	break;
        }
    }
    

	return 0;
}