Sum of ones

input/code.cpp: In function 'int countSetBits(int)':
input/code.cpp:23:17: error: 'pow' was not declared in this scope
   23 |     return (x * pow(2, (x - 1))) + (n - pow(2, x) + 1)
      |                 ^~~

#include <algorithm>
#include <iostream>
#include <queue>
#include <vector>

using namespace std;


int findLargestPower(int n)
{
    int x = 0;
    while ((1 << x) <= n)
        x++;
    return x - 1;
}

int countSetBits(int n)
{
    if (n <= 1)
        return n;
    int x = findLargestPower(n);
    return (x * pow(2, (x - 1))) + (n - pow(2, x) + 1)
           + countSetBits(n - pow(2, x));
}

int main()
{
    int x;
    cin >> x;
    cout << countSetBits(x) << endl;
    return 0;
}