Leetcode 1680

class Solution {
public:
    int concatenatedBinary(int n) {

        unsigned long long val = 0;
        int big_prime = 1e9 + 7;
        int bin_power = 1;
        int bin_digits = 0;

        for(int i = 1; i <= n; ++i){
            if(i > (bin_power-1)){
                bin_power = bin_power << 1;
                bin_digits++;
            }
            val = ((val << bin_digits) + i) % big_prime;
        }
    return val;
    }
};