import sys

H,W=map(int,input().split())
A=[list(map(int,list(input()))) for i in range(H)]

for i in range(H):
    if 0<A[i].count(1)<W:
        continue
    else:
        break
else:
    print("YES")
    sys.exit()

for i in range(W):
    count=0
    for j in range(H):
        if A[j][i]==1:
            count+=1
    if 0<count<H:
        continue
    else:
        break
else:
    print("YES")
    sys.exit()

print("NO")