#include <cstdio>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <cctype>
#include <utility>
#include <queue>
#include <cmath>

using namespace std;

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPII;
typedef pair<LL, LL> PLL;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;
typedef double DB;
typedef long double LD;
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define bit(x) (1 << (x))
#define bitl(x) (1LL << (x))
#define sqr(x) ((x) * (x))
#define sz(x) ((int)(x.size()))
#define counti(x) (__builtin_popcount(x))
#define countl(x) (__builtin_popcountll(x))
#define rep(i, n) for (int (i) = 0; (i) < (int)(n); ++(i))
#define X first
#define Y second

template <typename T, typename U> 
inline void chkmax(T& x, U y) {
    if (x < y) x = y;
}

template <typename T, typename U>
inline void chkmin(T& x, U y) {
    if (y < x) x = y;
}
int get() {
    char c;
    while (c = getchar(), (c < '0' || c > '9') && (c != '-'));
    bool flag = (c == '-');
    if (flag) c = getchar();
    int x = 0;
    while (c >= '0' && c <= '9') {
        x = x * 10 + c - 48;
        c = getchar();
    }
    return flag ? -x : x;
}

void output(int x) {
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    int len = 0, data[20];
    while (x) {
        data[len++] = x % 10;
        x /= 10;
    }
    if (!len) data[len++] = 0;
    while (len--) putchar(data[len] + 48);
    putchar('\n');
}
#define MX 1005
VI con[MX];
int chk[MX], T;
int ring[MX], prev[MX], Q[MX];
int n;
void DFS(int id) {
    int i;
    for (i = 0; i < con[id].size(); i++) {
        int j = con[id][i];
        if (chk[j] == T) continue;
        chk[j] = T;
        DFS(j);
    }
}
int Find(int id, int prev) {
    int i;
    for (i = 0; i < con[id].size(); i++) {
        int j = con[id][i];
        if (j == prev) continue;
        if (chk[j] == T) return j;
        if (chk[j] < T) chk[j] = T;
        return Find(j, id);
    }
}
int calc(int id, int des, int prev) {
    int i;
    if (id == des) return 0;
    for (i = 0; i < con[id].size(); i++) {
        int j = con[id][i];
        if (j == prev) continue;
        return calc(j, des, id) + 1;
    }
}
bool BFS(int st, int en) {
    int hd, tl;
    hd = tl = 0;
    Q[tl++] = st;
    T++;
    chk[st] = T;
    while (hd < tl) {
        int x = Q[hd++];
        if (x == en) break;
        int i;
        for (i = 0; i < con[x].size(); i++) {
            int j = con[x][i];
            if (chk[j] == T) continue;
            chk[j] = T;
            prev[j] = x;
            Q[tl++] = j;
        }
    }
    VI v;
    int i;
    for (i = en; i != st; i = prev[i]) {
        if (con[i].size() == 3) v.pb(i);
    }
    if (v.size() == 0) return true;
    if (v.size() == 1) {
        int x = v[0];
        for (int j = 0; j < con[x].size(); j++) if (con[x][j] == x) return true;
        return false;
    }
    if (v.size() > 2) return false;
    int x = v[0];
    for (int j = 0; j < con[x].size(); j++) if (con[x][j] == v[1]) return true;
    return false;
}
int main() {
    
    while (scanf("%d", &n) > 0) {
        int u, v;
        T++;
        int i;
        for (i = 0; i < n; i++) con[i].clear();
        for (i = 0; i < n; i++) {
            u = get(), v = get();
            u--, v--;
            if (u != v) con[u].pb(v), con[v].pb(u);
            else con[u].pb(v);
        }
        chk[0] = T;
        DFS(0);
        for (i = 0; i < n; i++) if (chk[i] < T || con[i].size() > 3) break;
        if (i < n) {
            
            puts("NO");
            continue;
        }
        int c = 0;
        VI V;
        for (i = 0; i < n; i++) if (con[i].size() == 1) c++, V.pb(i);
        if (c == 0 || c == 1) {
            
            puts("YES");
            continue;
        }
        if (c > 2) {
            
            puts("NO");
            continue;
        }
        if (BFS(V[0], V[1])) puts("YES");
        else puts("NO");
    }
    return 0;
}