505

A binary matrix is called good if every even length square sub-matrix has an odd number of ones.

Given a binary matrix a consisting of n rows and m columns, determine the minimum number of cells you need to change to make it good, or report that there is no way to make it good at all.

All the terms above have their usual meanings — refer to the Notes section for their formal definitions.

Input

The first line of input contains two integers n and m (1 ≤ n ≤ m ≤ 10^6 and n⋅ m ≤ 10^6) — the number of rows and columns in a, respectively.

The following n lines each contain m characters, each of which is one of 0 and 1. If the j-th character on the i-th line is 1, then a_{i,j} = 1. Similarly, if the j-th character on the i-th line is 0, then a_{i,j} = 0.

Output

Output the minimum number of cells you need to change to make a good, or output -1 if it's not possible at all.

Examples

Input

3 3 101 001 110

Output

2

Input

7 15 000100001010010 100111010110001 101101111100100 010000111111010 111010010100001 000011001111101 111111011010011

Output

-1

Note

In the first case, changing a_{1,1} to 0 and a_{2,2} to 1 is enough.

You can verify that there is no way to make the matrix in the second case good.

Some definitions —

• A binary matrix is one in which every element is either 1 or 0.
• A sub-matrix is described by 4 parameters — r_1, r_2, c_1, and c_2; here, 1 ≤ r_1 ≤ r_2 ≤ n and 1 ≤ c_1 ≤ c_2 ≤ m.
• This sub-matrix contains all elements a_{i,j} that satisfy both r_1 ≤ i ≤ r_2 and c_1 ≤ j ≤ c_2.
• A sub-matrix is, further, called an even length square if r_2-r_1 = c_2-c_1 and r_2-r_1+1 is divisible by 2.

inputFormat

Input

The first line of input contains two integers n and m (1 ≤ n ≤ m ≤ 10^6 and n⋅ m ≤ 10^6) — the number of rows and columns in a, respectively.

The following n lines each contain m characters, each of which is one of 0 and 1. If the j-th character on the i-th line is 1, then a_{i,j} = 1. Similarly, if the j-th character on the i-th line is 0, then a_{i,j} = 0.

outputFormat

Output

Output the minimum number of cells you need to change to make a good, or output -1 if it's not possible at all.

Examples

Input

3 3 101 001 110

Output

2

Input

7 15 000100001010010 100111010110001 101101111100100 010000111111010 111010010100001 000011001111101 111111011010011

Output

-1

Note

In the first case, changing a_{1,1} to 0 and a_{2,2} to 1 is enough.

You can verify that there is no way to make the matrix in the second case good.

Some definitions —

• A binary matrix is one in which every element is either 1 or 0.
• A sub-matrix is described by 4 parameters — r_1, r_2, c_1, and c_2; here, 1 ≤ r_1 ≤ r_2 ≤ n and 1 ≤ c_1 ≤ c_2 ≤ m.
• This sub-matrix contains all elements a_{i,j} that satisfy both r_1 ≤ i ≤ r_2 and c_1 ≤ j ≤ c_2.
• A sub-matrix is, further, called an even length square if r_2-r_1 = c_2-c_1 and r_2-r_1+1 is divisible by 2.

样例

3 3
101
001
110

2

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