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# Concatenation of Consecutive Binary Numbers

Updated: Mar 25, 2021

Given an integer n, return the decimal value of the binary string formed by concatenating the binary representations of 1 to n in order, modulo 109 + 7.

Example 1:

`Input: n = 1 Output: 1 Explanation: "1" in binary corresponds to the decimal value 1.  `

Example 2:

```Input: n = 3
Output: 27
Explanation: In binary, 1, 2, and 3 corresponds to "1", "10", and "11". After concatenating them, we have "11011", which corresponds to the decimal value 27. ```

Example 3:

```Input: n = 12
Output: 505379714
Explanation: The concatenation results in "1101110010111011110001001101010111100". The decimal value of that is 118505380540. After modulo 109 + 7, the result is 505379714.
```

Constraints:

• 1 <= n <= 105

Solution:

```class Solution {
public int concatenatedBinary(int n) {
int mod = 1_000_000_007;
int result = 0,pow=1;
for(int i=n;i>0;i--)
{
int no = i;
while(no>0)
{
if((no&1)==1) result = (result+pow)%mod;
no=no>>1;
pow = (pow*2)%mod;
}

}
return result;
}
}```