#!/usr/bin/python3
import sys
n, m = [int(v) for v in sys.stdin.readline().split(' ')]
g = [sys.stdin.readline() for _ in range(n)]

for j in range(m):
  ok = False
  for i in range(n):
    if g[i][j] == '1':
      ok = True
      break
  if not ok:
    sys.exit(1)

sys.exit(42)