Tanssiaiset

#include <iostream>
#include <vector>

using namespace std;

const int N = 1e5 + 5;

vector<pair<int, int> > pairs;
int amount[N];


int main() {
	int n;
	cin >> n;
	for(int i = 0; i <= n/2; ++i) {
		int a, b;
		cin >> a >> b;
		++amount[a];
		++amount[b];
		pairs.push_back(make_pair(a, b));
	}

	int firs = 0;
	int secon = 0;
	for(int i = 1; i <= n; ++i) {
		if(amount[i] > 1) {
			if(firs == 0) {
				firs = i;
			} else {
				secon = i;
				break;
			}
		}
	}

	for(int i = 0; i <= n/2; ++i) {
		int f = pairs[i].first;
		int s = pairs[i].second;
		if(f == firs && s == secon) {
			cout << f << " " << s << "\n";
			return 0;
		} else if (f == secon && s == firs) {
			cout << f << " " << s << "\n";
			return 0;
		}

	}

}

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