#include <bits/stdc++.h>
using namespace std;

#define For(i, a, b) for(int i = (a); i < (b); i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(int i = (a); i >= (b); i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
#define SZ(v) ((int)(v).size())

using lint = long long;
using ld = long double;

int INF = 2000000000;
lint LINF = 1000000000000000000;

struct SetupIo {
    SetupIo() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
        cout << fixed << setprecision(15);
        cerr << fixed << setprecision(15);
    }
} setupio;

// a <- max(a, b)
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

// a <- min(a, b)
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

int main() {
    int N;
    cin >> N;
    map<string, int> mp;
    vector<string> S(N), T(N);
    rep(i, N) {
        cin >> S[i] >> T[i];
        mp[S[i]]++;
        mp[T[i]]++;
    }
    bool ok = true;
    rep(i, N) {
        if (mp[S[i]] > 1 && mp[T[i]] > 1) {
            ok = false;
        }
    }
    cout << (ok ? "Yes\n" : "No\n");
}