#include <iostream>
#include <fstream>

const char inFile[] = "fact.in";
const char outFile[] = "fact.out";

using namespace std;

int main()
{
    ifstream fin(inFile);
    ofstream fout(outFile);
    long i, s, j, p;
    fin >> p;
    if (p==0) fout<<1;
    else if (p<5) fout<<5*p;
    else for (i=p*4;i<=p*5;i=i+5)
    {
        s = 0;
            for(j = 5; j <= i; j = j * 5)
                s = s + i / j;
            if(s > p) {
                fout << -1;
                break;
            }
            else if (s == p) {
                fout << i / 5 * 5;
                break;
            }
    }
 }