#include <fstream>
using namespace std; 
int five(int &n)
{
int nr=0;
while (n>=5)
{
	n=n/5;
	nr++;
}
return nr;
}
 
int main()
{
    ifstream f ( " fact.in " ); 
    ofstream g ( " fact.out " ); 
    int div2,p,i;
    f >> p; 
    for (i=0,p2=1<<30;p2>0;p2/=2)
        if (five(i+div2)<p)
            i=i+div2;
    if (five(i+1)==p)
        g << i+1; 
    else
        g <<-1;
}