// yukicoder: No.483 マッチ並べ
// 2019.7.21 bal4u

#include <stdio.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() {   // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

/* UNION-FIND library */
#define MAX  12900     // > 100*128 + 100
int id[2][MAX+5], size[2][MAX+5];
void init(int n) {
	int i, k; for (k = 0; k < 2; k++) for (i = 0; i < n; i++) id[k][i] = i, size[k][i] = 1;
}
int root(int k, int i) { while (i != id[k][i]) id[k][i] = id[k][id[k][i]], i = id[k][i]; return i; }
int connected(int k, int p, int q) { return root(k, p) == root(k, q); }
void unite(int k, int p, int q) {
    int i = root(k, p), j = root(k, q); if (i == j) return;
    if (size[k][i] < size[k][j]) id[k][i] = j, size[k][j] += size[k][i];
	else id[k][j] = i, size[k][i] += size[k][j];
}

int N;
int a[102], b[102];
char f[MAX+5];

int main()
{
	int i, r;
	
	N = in(); init(MAX);
	for (i = 0; i < N; i++) {
		r = in() << 7, a[i] = r | in();
		r = in() << 7, b[i] = r | in();
		unite(0, a[i], b[i]);
	}
	
	for (i = 0; i < N; i++) {
		if (connected(1, a[i], b[i])) {
			if (++f[root(0, a[i])] >= 2) { puts("NO"); return 0; }
		} else unite(1, a[i], b[i]);
	}
	puts("YES");
	return 0;
}