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

#define rep_(i, a_, b_, a, b, ...) for (int i = (a), lim##i = (b); i < lim##i; ++i)
#define rep(i, ...) rep_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define drep_(i, a_, b_, a, b, ...) for (int i = (a) - 1, lim##i = (b); i >= lim##i; --i)
#define drep(i, ...) drep_(i, __VA_ARGS__, __VA_ARGS__, __VA_ARGS__, 0)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#ifdef LOCAL
void debug_out() {
    cerr << endl;
}
template <class Head, class... Tail> void debug_out(Head H, Tail... T) {
    cerr << ' ' << H;
    debug_out(T...);
}
#define debug(...) cerr << 'L' << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define dump(x) cerr << 'L' << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif
using ll = long long;
using ld = long double;
template <class T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
template <class T> vector<T> make_vec(size_t n, T a) {
    return vector<T>(n, a);
}
template <class... Ts> auto make_vec(size_t n, Ts... ts) {
    return vector<decltype(make_vec(ts...))>(n, make_vec(ts...));
}
template <class T> inline void fin(const T x) {
    cout << x << '\n';
    exit(0);
}
template <class T> inline void deduplicate(vector<T> &a) {
    sort(all(a));
    a.erase(unique(all(a)), a.end());
}
template <class T> inline bool chmin(T &a, const T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T> inline bool chmax(T &a, const T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T> inline int sz(const T &x) {
    return x.size();
}
template <class T> inline int count_between(const vector<T> &a, T l, T r) {
    return lower_bound(all(a), r) - lower_bound(all(a), l);
}
template <class T1, class T2> istream &operator>>(istream &is, pair<T1, T2> &p) {
    is >> p.first >> p.second;
    return is;
}
template <class T1, class T2> ostream &operator<<(ostream &os, pair<T1, T2> &p) {
    os << '(' << p.first << ", " << p.second << ')';
    return os;
}
template <class T, size_t n> istream &operator>>(istream &is, array<T, n> &v) {
    for (auto &e : v) is >> e;
    return is;
}
template <class T, size_t n> ostream &operator<<(ostream &os, array<T, n> &v) {
    for (auto &e : v) os << e << ' ';
    return os;
}
template <class T> istream &operator>>(istream &is, vector<T> &v) {
    for (auto &e : v) is >> e;
    return is;
}
template <class T> ostream &operator<<(ostream &os, vector<T> &v) {
    for (auto &e : v) os << e << ' ';
    return os;
}
template <class T> istream &operator>>(istream &is, deque<T> &v) {
    for (auto &e : v) is >> e;
    return is;
}
template <class T> ostream &operator<<(ostream &os, deque<T> &v) {
    for (auto &e : v) os << e << ' ';
    return os;
}
inline ll floor_div(ll x, ll y) {
    if (y < 0) x = -x, y = -y;
    return x >= 0 ? x / y : (x - y + 1) / y;
}
inline ll ceil_div(ll x, ll y) {
    if (y < 0) x = -x, y = -y;
    return x >= 0 ? (x + y - 1) / y : x / y;
}
inline int floor_log2(const ll x) {
    assert(x > 0);
    return 63 - __builtin_clzll(x);
}
inline int ceil_log2(const ll x) {
    assert(x > 0);
    return (x == 1) ? 0 : 64 - __builtin_clzll(x - 1);
}
inline int popcount(const ll x) {
    return __builtin_popcountll(x);
}
struct fast_ios {
    fast_ios() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
    };
} fast_ios;

// 時間計測
auto system_now = std::chrono::system_clock::now();
int check_time() {
    auto now = std::chrono::system_clock::now();
    return std::chrono::duration_cast<std::chrono::milliseconds>(now - system_now).count();
}

// 乱数
struct Xorshift {
    uint32_t x = 123456789, y = 362436069, z = 521288629, w = 88675123;

    uint32_t rand_int() {
        uint32_t t = x ^ (x << 11);
        x = y;
        y = z;
        z = w;
        return w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
    }

    // 0以上mod未満の整数を乱択
    uint32_t rand_int(uint32_t mod) {
        return rand_int() % mod;
    }

    // l以上r未満の整数を乱択
    uint32_t rand_int(uint32_t l, uint32_t r) {
        assert(l < r);
        return l + rand_int(r - l);
    }

    // 0以上1以下の実数を乱沢
    double rand_double() {
        return (double)rand_int() / UINT32_MAX;
    }
};
Xorshift xor_shift;

// constexpr int INF = numeric_limits<int>::max() >> 2;
// constexpr ll INFll = numeric_limits<ll>::max() >> 2;
// constexpr ld EPS = 1e-10;
// const ld PI = acos(-1.0);
// using mint = modint998244353;
// using mint = modint1000000007;
// using mint = modint;
// using Vm = V<mint>; using VVm = VV<mint>;

int main() {
    int N;
    cin >> N;
    map<string, int> cnt;
    vector<vector<string>> S(N, vector<string>(2));
    rep(i, N) {
        cin >> S[i][0] >> S[i][1];
        cnt[S[i][0]]++;
        cnt[S[i][1]]++;
    }

    bool ok = true;
    rep(i, N) {
        if (cnt[S[i][0]] > 1 && cnt[S[i][1]] > 1) {
            ok = false;
            break;
        }
    }

    cout << (ok ? "Yes" : "No") << endl;

    return 0;
}