#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    long p,n,k,pp,i;
    int c,ok;
    ifstream f("factorial.in");
    ofstream g("factorial.out");
    f>>p;
    ok=0;
    for(n=0;n<=100000000;n++){
                           k=0;
                           for(i=n;i<=n;i++){
                                            pp=pp*i;
                                            }
                           c=pp%10;
                           pp=pp/10;
                           while(c==0){
                                      k=k+1;
                                      c=pp%10;
                                      pp=pp/10;
                                      }
                           if(k==p){
                                   ok=1;
                                   }
                           if(ok==1){
                                    break;
                                    }
    }
    g<<n;
    f.close();
    g.close();
    return 0;
}