#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

void factorial(int n){
    int i = 1,k = 1;
    while(n > 0){
        k++;
        i = i * k;
        while(i % 10 == 0){
            n -= 1;
            i /= 10;
        }
        i = i % 1000;
    }
    out << k;
}

int main(){
    int n;
    in >> n;
    if(n == 0)
        out << "1";
    else
        factorial(n);
    
    return 0;
}