#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define mod ((int)1e9+7)
#define lim 1000000000000000007
#define lim1 18446744073709551615  //Unsigned
#define sq(a) ((a)*(a))
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define mms(v,i) memset(v,i,sizeof(v))
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define REP(i,a,b) for (int i = a; i <= b; i++)
#define REPN(i,a,b) for (int i = a; i >= b; i--)
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;
typedef pair<int,int> pi;
typedef pair<ll,ll> PL;
typedef pair<ll,int> PLI;
typedef pair<int,ll> PIL;
typedef pair<int,pair<int,int> > pii;
typedef pair<double,double> pdd;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
ll power(ll a,ll b) {
   a %= mod;
   ll res=1;
   while(b){
      if(b%2==1) res=(res*a)%mod;
      a=(a*a)%mod;
      b>>=1;
   }
   return res;
}
ll gcdll(ll a,ll b) {
    if (b==0) return a;
    return gcdll(b,a%b);
}
int gcd(int a,int b) {
    if (b==0) return a;
    return gcd(b,a%b);
}

struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

const int N = (int)2e5+5;
const int M = (int)3e3+5;
const int Q = 301;
const int logN = 19;

bool check(pi a, pi b) {
  int num = (b.second - a.second);
  int den = (b.first - a.first);
  return (abs(num)<=abs(den));
}
void solve() {
  int n;
  cin >> n;
  vector<pi> points(n);
  int ans = 0;
  REP(i,0,n-1) {
    cin >> points[i].first >> points[i].second;
    REP(j,0,i-1) {
      if(check(points[i],points[j])) {
        ans++;
      }
    }
  }
  cout << ans;
}
int main() {
    //freopen("output.txt","r",stdin);
    //freopen("output.txt","w",stdout);

    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int T=1;
    // cin>>T;
    REP(TC,1,T) {
        //cout<<"Case #"<<TC<<": ";
        solve();
        cout<<"\n";
    }
}

#include <iostream> // cout, endl, cin
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <cstdint> // int64_t, int*_t
#include <cstdio> // printf
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
#include <stack> // stack
#include <deque> // deque
#include <unordered_map> // unordered_map
#include <unordered_set> // unordered_set
#include <bitset> // bitset
#include <cctype> // isupper, islower, isdigit, toupper, tolower



using ll=  long long ;

#define rep(i,n)  for(int i=0;i<(n);i++)
#define f first
#define sc second


int fact(int n){
if(n==0){
     return 1;
 }else{
     return n*fact(n-1);
 }
}

bool is_prime(int x){
if(x<=1) return false;
for(int i=2;i*i<x;i++){
    if(x%i==0) return false;}
return true;}

template<class T>void chmin(T& a,T b){
    if(a>b){
        a=b;
    }
}

template<class T>void chmax(T& a,T b){
    if(a<b){
        a=b;
    }
}
int gcd(int x, int y) {
     if(x % y == 0) {
        return y;
     } else {
        return gcd(y, x % y); 
     }
}

ll f(ll x,ll c,ll d){
    return x-x/c-x/d+x/(c/(gcd(c,d))*d);
}



using namespace std;
int main(){
   int n;
   cin>>n;

   set<string> t;

   string s[n];

   rep(i,n){
       cin>>s[i];
       t.insert(s[i]);
   }

   bool ok=false;

   rep(i,n){
       if(t.count('!'+s[i])){
           cout << s[i] << endl;
           ok=true;
           return 0;
       }
   }

   cout << "satisfiable" << endl;


  
  
}