#include<fstream>   
#include<iostream>   
using namespace std;   
  
int main()   
{   
ifstream f1("fact.in");   
ofstream f2("fact.out");   
register long n;   
f1>>n;   
  
if(n==0){f2<<1;f2.close();return 0;}   
  
  
register long i, x = 0, nr, j;   
for(i=5;;i+=5)   
{   
    nr = 0;   
    j = i;   
    while(j)   
    {   
        if(j%5==0)nr++;   
        else break;   
        j/=5;   
    }   
    x += nr;   
    if(x>=n)break;   
}   
if(x!=n)i=-1;    
f2<<i;   
cout<<i;   
f1.close();   
f2.close();   
return 0;}