#include <fstream>

using namespace std;

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

int factorial(int P)
{
    long long int nr=1, aux;
    unsigned int b=0;
    for(long int i=1;i<=15;i++){b=0;
                                       nr=nr*i;
                                       aux=nr;
                                       while(aux%10==0){b++;
                                                        aux=aux/10;}
                                       if(b==P)return i;}
}
    
int main()
{
    int P;
    in>>P;
    out<<factorial(P)<<" ";
    return 0;
}