Where is bug? What is wrong?

lesson_1.8.13.cpp

#include <iostream>
using namespace std;

int log(int a)
{
    int cnt;
    while (a > 1)
    {
        a /= 2;
        cnt++;
    }
    
    return cnt;
}

int main()
{
    int t, a;
    cin >> t;

    while (t-- > 0)
    {
        cin >> a;
        cout << log(a) << endl;
    }
    
    return 0;
}