inp = open("input.txt")
out = open("output.txt", "w")
pos, n = [int(x) for x in inp.readline().split()]
a = []
for i in range(n):
  a.append([int(x) for x in inp.readline().split()][::-1])
a.sort(reverse=True)
for i in range(n):
  if pos == a[i][1]:
    pos += 1
  elif pos == a[i][1] + 1:
    pos -= 1
out.write(str(pos))