#include <bits/stdc++.h>
#define ll long long
#define val 1000000000000
using namespace std;
 
ll a[1000002];
 
ll minm(ll x, ll y)
{
    if(x < y) return x;
    return y;
}
 
int main()
{
   // freopen("input_output\\in09.txt", "r", stdin);
    //freopen("input_output\\out09.txt", "w", stdout);
    int t;
    cin >> t;
    //assert(1 <= t && t <= 100);
    while (t--) {
        int n, z;
        cin >> n >> z;
        //assert(1 <= n && n <= 10000);
        //assert(1 <= z && z <= n);
        for (int i = 1; i <= n; i++) {
            cin >> a[i];
           // assert(0 <= a[i] && a[i] <= val);
        }
        ll prev = 0;
        int prevptr = 1;
        int currptr = z + 1;
        for (int i = 1; i <= z; i++) prev ^= a[i];
        ll ans_val = prev;
        int ans = prevptr;
        //cout << prev << " ";
        while ((currptr - prevptr == z) && (currptr <= n) ) {
            prev ^= a[prevptr];
            prev ^= a[currptr];
            ans_val = minm(prev, ans_val);
            if(ans_val == prev) {
                ans = prevptr + 1;
            }
           // cout << prev << " ";
            prevptr++;
            currptr++;
        }
        //cout << endl;
        cout << ans << endl;
    }
}
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