#include <fstream.h>
#include <iomanip.h>

fstream fin("fact.in",ios::in);
fstream fout("fact.out",ios::out);
long n,i,nr,p,t;
int main(){
fin>>p; 
for(i=0;nr<p;i+=5)
    {
    nr=0;
    n=5;
    while (n<=i) 
        {
        nr+=i/n;
        n*=5;    
        }    
    } 
if (p==0) i=1;   
if (nr==p)
    fout<<i-5;
else
    fout<<-1;
fin.close();fout.close();  
return 0; 
}