#include<bits/stdc++.h>

#define all(s) s.begin(),s.end()
#define rc(x) return cout<<x<<endl,0
#define forn(i,n) for(int i=0;i<int(n);i++)
#define len(a) (int) (a).size()

#define pb push_back
#define mp make_pair
#define fr first
#define sc second

typedef long long ll;
typedef long double ld;

const int nmax=1e5+3;
const int mod=998244353;
const ll inf=0x3f3f3f3f3f3f3f3f;

/*===================*\
      comentarii:
\*===================*/

using namespace std;

int zerouri(int p)
{
    int aux=0;
    while(p>=5)
    {
        aux+=p/5;
        p/=5;
    }
    return aux;
}

int cb(int st, int dr,int n)
{
    int mid,sol=-1;

    while(st<=dr)
    {
        mid=(st+dr)/2;
        int nr=zerouri(mid);
        if(nr==n) sol=mid;
        if(nr<n) st=mid+1; else dr=mid-1;
    }
    return sol;
}

int main()
{
    //freopen("bfs.in","r",stdin);
    //freopen("bfs.out","w",stdout);
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    int n;
    fin>>n;
    int st=1,dr=500000000;
    fout<<cb(st,dr,n);
}