# include<bits/stdc++.h>

using namespace std;
# define l long long 
# define db long double 
# define rep(i,a,b) for(l i=a;i<b;i++)
# define vi vector<l>
# define vvi vector<vi>
# define vsi vector<set<l> >
# define pb push_back
# define mp make_pair
# define ss second
# define ff first
# define pii pair<l,l>
# define trvi(v,it) for(vi::iterator it=v.begin();it!=v.end();++it)
# define read(a) freopen(a,"r",stdin)
# define write(a) freopen(a,"w",stdout)
# define io ios::sync_with_stdio(false)

template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ' ' << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
 

#ifdef KRISHNAN_DEBUG
void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

const bool MULTIPLE_TEST_CASES = false;

const l MOD=1e9+7;
const l N=1e5+5;
const l INF=1e12;
db PI = 3.141592653589793238;

void solve() {
	l n;
	cin>>n;
	l x0,y0;
	cin>>x0>>y0;
	l xn,yn;
	cin>>xn>>yn;

	db xmid = (db)(x0+xn)/2, ymid = (db)(y0+yn)/2;

	l xDiff = xn-x0, yDiff=yn-y0;
	dbg(xDiff, yDiff);
	db angle = acos((db)xDiff / (sqrtl(xDiff*xDiff + yDiff*yDiff)));
	dbg(angle, angle*180/PI);
	if(yDiff<0) {
		angle = 2*PI-angle;
	}
	dbg(angle, angle*180/PI);
	angle += 2*PI/n;
	dbg(angle, angle*180/PI);
	// angle = PI-angle;
	dbg(angle);
	db length = sqrtl(xDiff*xDiff + yDiff*yDiff) / 2;
	db X = xmid - length*cos(angle);
	db Y = ymid - length*sin(angle);
	cout.precision(15);
	cout<<X<<" "<<Y<<"\n";


	return;
}


int main(){
	io;
	int t=1;
	if (MULTIPLE_TEST_CASES) cin>>t;
	rep(i,0,t) {
		solve();
	}

	return 0;
}

#include<bits/stdc++.h>
using namespace std;

#define ll              long long
#define deb(x)          cout << #x << "=" << x << endl
#define deb2(x, y)      cout << #x << "=" << x << " , " << #y << "=" << y << endl
#define _               ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);

void solve()
{
    ll n, m;
    cin >> n;
    vector<pair<ll,ll>>v;

    for(int i=0 ; i<n ; i++)
    {
    	ll x,y;
    	cin >> x >> y;
    	v.push_back({x,y});
    }

    ll res = 0;

    for(int i=0 ; i<n ; i++)
    {
    	for(int j=i+1; j<n ; j++)
    	{
    		double slope = ((double)(v[i].second-v[j].second)/(double)(v[i].first-v[j].first));

    		if(slope >= -1 && slope <= 1) res++;
    	}
    }
    cout << res << '\n';
}


int main()
{_
    int t = 1;

    //cin >> t;

    while(t--)
    {
        solve();
    }

    return 0;
}