#include<fstream>
using namespace std;
#define oo 999999999
int zero(int n)
{
int x=0,p=5;
while(n/p!=0)
{
x+=n/p;
p*=5;
}
return x;
}
int caut(int n)
{
int min=0, max=oo,m,t;
while(min<=max)
{
m=min+(max-min)/2;
t=zero(m);
if(t==n)
return m-m%5;
if(t>n)
max=m-1;
else min=m+1;
}
return -1;
}
int main()
{
int n,x;
ifstream fin("fact.in");
ofstream fout("fact.out");
fin>>n;
if(n==0)
fout<<1;
else
fout<<caut(n);
fin.close();
fout.close();
}