N, M = map(int, input().split())
query = [list(input().split()) for _ in range(M)]

for num in range(10**N):
    if len(str(num)) != N:
        continue
    else:
        cnt = 0
        s = str(num)
        for sc in query:
            if s[int(sc[0])-1] == sc[1]:
                cnt += 1
        if cnt == M:
            ans = num
            break
print(ans)