#coding=utf-8 import sys Di=[]#难度 line_1 = sys.stdin.readline().strip() N_M = map(int, line_1.split()) N=N_M[0] m=N_M[1] for i in range(N): line = sys.stdin.readline().strip() values = map(int, line.split()) Di.append(values) line_last = map(int, sys.stdin.readline().strip().split()) Di.sort(key=lambda x: x[1], reverse=True) for i in line_last: maxx = 0 for j in Di: if i<j[0]: continue else: maxx=j[1] print maxx break if maxx==0: print 0