英文题看不懂

Time Limit: 1000 ms Memory Limit: 65536 KiB

Problem Description

Let's define logical OR as an operation on two logical values (i. e. values that belong to 
the set {0, 1}) that is equal to 1 if either or both of the logical values is set to 1, otherwise it is 0. We can define logical OR of 
three or more logical values in the same manner:
 
where  is equal to 1 if some ai = 1, otherwise it is equal to 0.
 
Nam has a matrix A consisting of m rows and n columns. The rows are numbered from 1 to m,
 columns are numbered from 1 to n. Element at row i (1≤ i≤ m) and column j (1≤ j≤ n) is denoted as Aij. 
All elements of A are either 0 or 1. From matrix A, Nam creates another matrix B of the same size using formula:
 
(Bij is OR of all elements in row i and column j of matrix A)
 
 
 
Nam gives you matrix B and challenges you to guess matrix A. Although Nam is smart, he could
 probably make a mistake while calculating matrix B, since size of A can be large.

Input

 The first line contains two integer m and n (1 ≤ m,n ≤ 100), number of rows and number of columns of matrices respectively.

 

The next m lines each contain n integers separated by spaces describing rows of matrix B (each element of B is either 0 or 1).

Output

 In the first line, print "NO" if Nam has made a mistake when calculating B, otherwise print "YES".

Sample Input

2 2
1 0
0 0
2 3
1 1 1
1 1 1

Sample Output

NO
YES

Hint

 

Source

scf0920