n,m=map(int,input().split())
arr=[list(map(int,input().split())) for _ in range(m)]
if n==1:
  for i in range(10):
    tmp=str(i)
    flag=True
    for j in range(m):
      if tmp[arr[j][0]-1]!=str(arr[j][1]):
        flag=False
    if flag==True:
      print(i)
      break
else:
  for i in range(10**(n-1),10**n):
    tmp=str(i)
    flag=True
    for j in range(m):
      if tmp[arr[j][0]-1]!=str(arr[j][1]):
        flag=False
    if flag==True:
      print(i)
      break