#include <fstream>

using namespace std;

int main()
{
    ifstream fin ("factorial.in");
    ofstream fout ("factorial.out");
    int p, i, s, j;
    fin>>p;
    if(p==0)
        fout<<"0";
    else if(p<5)
        fout<<p*5;
        else
    {
        i=p*4;
        while(1==1)
        {
            s=0;
            for(j=5;j<=i;j*=5)
                s=s+i/j;
            if(s>p)
            {
                fout<<"-1";
                return 0;
            }
            else if(s==p)
            {
                fout<<i-i%5;
                return 0;
            }
            i+=5;
        }
    }
    return 0;
}