Tanssiaiset

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define IO ios_base::sync_with_stdio(0); cin.tie(0)
#define ff first
#define ss second
#define pb push_back
#define INF 2147483647
#define LINF (1LL<<61LL)
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, ll> pil;

int n;
int v[101010];
pii p[101010];

int main() {
  IO; cin>>n;
  FOR(i,0,n/2+1) {
    int a,b; cin>>a>>b;
    p[i] = {a,b};
    v[a]++; v[b]++;
  }
  
  int a=0, b=0;
  FOR(i,1,n+1) {
    if (v[i] == 2) {
      if (a) b = i;
      else a = i;
    }
  }
  
  FOR(i,0,n/2+1) {
    if (p[i] == (pii){a,b} || p[i] == (pii){b,a}) {
      cout<<p[i].ff<<" "<<p[i].ss<<"\n";
    }
  }
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED