#include <bits/stdc++.h>
// #include <atcoder/all>
using namespace std;
// using namespace atcoder;
#define rep(i, a, n) for(int i = a; i < n; i++)
#define rrep(i, a, n) for(int i = a; i >= n; i--)
#define inr(l, x, r) (l <= x && x < r)
#define ll long long
#define ld long double

// using mint = modint1000000007;
// using mint = modint998244353;
constexpr int IINF = 1001001001;
constexpr ll INF = 1e18;

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

int main(){
    int n; cin >> n;
    vector<string> s(n), t(n);
    map<string, int> exist;
    rep(i, 0, n){
        cin >> s[i] >> t[i];
        exist[s[i]]++;
        exist[t[i]]++;
    }
    bool ok = true;
    rep(i, 0, n){
        if(exist[s[i]] >= 2 && exist[t[i]] >= 2) ok = false;
    }
    if(ok) cout << "Yes" << endl;
    else cout << "No" << endl;

    
    return 0;
}