#include <fstream>

using namespace std;

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

int factorial(unsigned int P)
{
    unsigned long int nr=1;
    unsigned int b=0;
    for(unsigned int i=1;i<=10000;i++){nr=nr*i;
                                       unsigned long int aux=nr;
                                       while(aux!=0){if(aux%10==0)b++;
                                                     else break;           
                                                     aux=aux/10;}
                                       if(b==P)return i;
                                       b=0;}
}
    
int main()
{
    unsigned int P;
    in>>P;
    out<<factorial(P)<<" ";
    return 0;
}