Problem:
Sorting Pairs

Write a program which print coordinates $(x_i, y_i)$ of given $n$ points on the plane by the following criteria.

first by $x$-coordinate

in case of a tie, by $y$-coordinate

Input

The input is given in the following format.

$n$
$x_0 \; y_0$
$x_1 \; y_1$
:
$x_{n-1} \; y_{n-1}$

In the first line, the number of points $n$ is given. In the following $n$ lines, coordinates of each point are given.

Output

Print coordinate of given points in order.

Constraints

$1 \leq n \leq 100,000$

$-1,000,000,000 \leq x_i, y_i \leq 1,000,000,000$

Sample Input 1

5
4 7
5 5
2 3
6 8
2 1

Sample Output 1

2 1
2 3
4 7
5 5
6 8

Solution in C++14 (judge verdict: Accepted)

#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vvll> vvvll;
typedef vector<ld> vld;
typedef vector<string> vstr;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef priority_queue<ll, vector<ll>, greater<ll>> spqll;  // 小さい順に取り出し
typedef priority_queue<ll, vector<ll>, less<ll>> bpqll;     // 大きい順に取り出し

#define REP(i, n) for (ll i = 0; i < (ll)(n); i++)
#define IREP(i, v) for (auto i = (v).begin(); i != (v).end(); ++i)
#define TS to_string
#define NP next_permutation
#define ALL(v) (v).begin(), (v).end()
#define endl "\n"

ll INF = 1e9;
ll MOD = 1000000007;
ll LINF = 1e18;
ld EPS = 1e-9;
ld PI = M_PI;
vll dx = {1, 0, -1, 0, 1, -1, -1, 1};
vll dy = {0, 1, 0, -1, 1, 1, -1, -1};
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a;} //最大公約数
ll lcm(ll a, ll b) { return a / gcd(a, b) * b;}     //最小公倍数

void yes(){ cout << "Yes" << endl;}
void no(){ cout << "No" << endl;}

//-----------------------------------------

//-----------------------------------------
int main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);

  ll n;
  cin >> n;
  vpll vec(n);
  REP(i,n) cin >> vec[i].first >> vec[i].second;
  sort(ALL(vec));
  REP(i,n) cout << vec[i].first << " " << vec[i].second <<endl;


  return 0;
}