# Different Bits Sum Pairwise

We define `f(X, Y)` as number of different corresponding bits in binary representation of X and Y. For example, `f(2, 7)` = 2, since binary representation of 2 and 7 are `010` and `111`, respectively. The first and the third bit differ, so `f(2, 7)` = 2.

You are given an array of N positive integers, A1, A2 ,…, AN. Find sum of f(Ai, Aj) for all pairs (i, j) such that 1 ≤ i, j ≤ N. Return the answer modulo 109+7.

For example,

```
A=[1, 3, 5]

We return

f(1, 1) + f(1, 3) + f(1, 5) + 
f(3, 1) + f(3, 3) + f(3, 5) +
f(5, 1) + f(5, 3) + f(5, 5) =

0 + 1 + 1 +
1 + 0 + 2 +
1 + 2 + 0 = 8
```

```java
public class Solution {
    public int cntBits(int[] A) {
        int n = A.length;
        long dist = 0;
        for (int i = 0; i < 31; i++) {
            int oneCount = 0;
            for (int j = 0; j < n; j++) 
                oneCount += (A[j] >> i & 1);
            int zeroCount = n - oneCount;
            dist = (dist + 2L * oneCount * zeroCount) % 1000000007;
        }
        return (int) dist;
    }
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://mayanktyagi3111.gitbook.io/interview-prep/bit-manipulation/different-bits-sum-pairwise.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.