#include <fstream>
#include <cmath>
using namespace std;
ifstream in ("fact.in");
ofstream out ("fact.out");
int main()
{   int n,p,v,pp;
    in>>p;
    for(n=p+1;n<=p*5;n++){
        pp=1; v=0;
        while(pow(5,pp)<=n){
            v+=n/pow(5,pp);
            pp++;}
        if(v==p){out<<n;
                 return 0;}}
    if(p==0) out<<"1";
    else out<<"-1";
    return 0;
}