#!/usr/bin/env python3
def main():
    h, w = map(int, input().split())
    f = [input() for _ in range(h)]
    p = True
    for y in range(h):
        if f[y].count('1') in (0, w):
            p = False
    g = [''.join([f[y][x] for y in range(h)]) for x in range(w)]
    q = True
    for x in range(w):
        if g[x].count('1') in (0, h):
            q = False
    ans = p or q
    print(ans and 'YES' or 'NO')
if __name__ == "__main__":
    main()