#include <fstream>
#define NMax 1000000000
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int fact (int x)
{
    int a=5,rez=0;
    while (x/a)
    {
        rez=rez+x/a;
        a=a*5;
    }
    return rez;
}
int main ()
{
    int p,val;
    in>>p;
    if (p==0) g<<1;
    else
    {
        int min=1,max=NMax,mij;
        int ok=0;
        while (min<=max && !ok)
        {
            mij=(min+max)/2;
            val=fact(mij);
            if (val<p) min=mij+1;
            else if (val>p) max=mij-1;
            else ok=1;
        }
        if (ok)
        {
            while (mij%5) mij--;
            out<<mij;
        }
        else out<<-1;
    }
	return 0;
}