#include<fstream>

 

using namespace std;

 

ifstream in("fact.in");

ofstream out("fact.out"); 

int hi, lo, mij, p;

 

int nr_zer(int nr)

{

unsigned int y = 0, c = 5;

 

while(nr>=c)

{

y+=nr/c;

c*=5;

}

return y;

}

 

 

int main()

{

in >> p;

 



 

lo = 1, hi = 5*p; while(lo <= hi )

{

mij = lo+(hi-lo)/2;

if(nr_zer(mij) < p)

lo = mij+1;

 

else hi = mij-1;

}

if(nr_zer(lo) != p)

out << -1;

else out << lo;

}