#include <string>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <list>
#include <stdexcept>
#include <functional>
#include <utility>
#include <iomanip>
#include <ctime>
#include <valarray>
#include <iostream>
#include <sstream>
#include <fstream>
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
#define MEM(a,b) memset((a),(b),sizeof(a))
const LL INF = 1e9 + 7;
const int N = 2e5 + 10;

int main()
{
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	int n;
	cin >> n;
	vector<pair<string, string>> vs(n);
	map<string, int> ms;
	for (auto& [s1, s2] : vs)
	{
		cin >> s1 >> s2;
		ms[s1]++;
		if (s1 != s2) ms[s2]++;
	}
	for (auto& [s1, s2] : vs)
	{
		if (ms[s1] > 1 && ms[s2] > 1)
			puts("No"), exit(0);
	}
	puts("Yes");
	return 0;
}