#include <bits/stdc++.h>
using namespace std;
// #include <atcoder/modint>
// using namespace atcoder;
// using mint = modint998244353;
using ll = long long;
#define fix(x) fixed << setprecision(x)
#define rep(i, n) for(int i = 0; i < n; ++i)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}
constexpr ll INFLL = (1LL << 62), MOD = 998244353;
constexpr int INF = (1 << 30);

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    map<string,int> mp1, mp2;
    bool f = true;
    vector<string> s(n), t(n);
    rep(i,n){
        cin >> s[i] >> t[i];
        ++mp1[s[i]];
        ++mp2[t[i]];
    }
    rep(i,n){
        if(mp1[s[i]]>1 && mp2[t[i]]>1) f = false;
    }
    cout << (f?"Yes\n":"No\n");
    return 0;
}