def main():
    import sys
    input = sys.stdin.read().split()
    
    ptr = 0
    N = int(input[ptr])
    ptr += 1
    M = int(input[ptr])
    ptr += 1
    S = []
    for _ in range(M):
        s = input[ptr].strip()
        ptr += 1
        S.append(s)
    
    mod = 10**18 + 3
    base = 911382629
    max_m = M
    power = [1] * (max_m + 1)
    for i in range(1, max_m + 1):
        power[i] = (power[i-1] * base) % mod
    
    hash_list = []
    for i in range(1, N+1):
        pos = N - i
        bits = []
        for s in S:
            bits.append(s[pos])
        bits_str = ''.join(bits)
        h = 0
        for c in bits_str:
            h = (h * base + int(c)) % mod
        hash_list.append(h)
    
    # Check all pairs
    for i in range(N):
        for j in range(i+1, N):
            if hash_list[i] == hash_list[j]:
                print("No")
                return
    
    print("Yes")

if __name__ == "__main__":
    main()