Establish equality

input/code.cpp: In function 'int main()':
input/code.cpp:46:18: error: redeclaration of 'uint64_t k'
   46 |         uint64_t k = a + (b - a) / 2;
      |                  ^
input/code.cpp:40:18: note: 'uint64_t k' previously declared here
   40 |         uint64_t k = a + (b - a) / 2;
      |                  ^

#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <stdint.h>
using namespace std;

bool isValidSolution(const vector<uint64_t>& bottles, uint64_t target)
{
    uint64_t deficit, surplus;
    deficit = surplus = 0;
    for (size_t i = 0; i < bottles.size(); i++)
    {
        if (bottles[i] < target)
        {
            deficit += target - bottles[i];
        }
        else
        {
            surplus += bottles[i] - target;
        }
    }
    return surplus >= 2 * deficit;
}

int main()
{
    uint64_t n;
    cin >> n;
    vector<uint64_t> bottles(n);
    for (size_t i = 0; i < n; i++)
    {
        cin >> bottles[i];
    }

    uint64_t bestSolution = 0;
    uint64_t a = 0, b = 1000000000;
    while (a <= b)
    {
        uint64_t k = a + (b - a) / 2;

        if (a == b)
        {
            k = a;
        }
        uint64_t k = a + (b - a) / 2;
        if (isValidSolution(bottles, k))
        {
                bestSolution = k;
            a = k + 1;
        }
        else
        {
            b = k - 1;
        }
    }
    cout << bestSolution << endl;
        

}