#include<fstream>
using namespace std;
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=999999999,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;
    ifstream in("fact.in");
    ofstream out("fact.out");
    in>>n;
    if(n==0) out<<1;
    else out<<caut(n);
    in.close();
	out.close();
	return 0;
}