| f | from collections import defaultdict | f | from collections import defaultdict |
| n | a = input() | n | room = input() |
| b = [] | | lab = [] |
| while 1: | | while 1: |
| n | if a.find(' ') == -1: | n | if room.find(' ') == -1: |
| break | | break |
| t | b.append(a) | t | lab.append(room) |
| a = input() | | room = input() |
| start = a | | start = room |
| end = input() | | finish = input() |
| z = defaultdict(set) | | lab2 = defaultdict(set) |
| for i in range(len(b)): | | for i in range(len(lab)): |
| (q, w) = b[i].split(' ') | | (x, y) = lab[i].split(' ') |
| z[q].add(w) | | lab2[x].add(y) |
| z[w].add(q) | | lab2[y].add(x) |
| e = set() | | lab3 = set() |
| for i in z[start]: | | for i in lab2[start]: |
| e.add(i) | | lab3.add(i) |
| for j in z[i]: | | for j in lab2[i]: |
| e.add(j) | | lab3.add(j) |
| for k in z[j]: | | for k in lab2[j]: |
| e.add(k) | | lab3.add(k) |
| for d in z[k]: | | for l in lab2[k]: |
| e.add(d) | | lab3.add(l) |
| for y in z[d]: | | for t in lab2[l]: |
| e.add(y) | | lab3.add(t) |
| for p in z[y]: | | for s in lab2[t]: |
| e.add(p) | | lab3.add(s) |
| if end in e: | | if finish in lab3: |
| print('YES') | | print('YES') |
| else: | | else: |
| print('NO') | | print('NO') |