#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
const i64 mod = 1000000007;
void solve() {
    i64 n,k;
    cin >> n >> k;
    vector<i64>a(n);
    for ( int i = 0 ; i < n ; i++ ) {
        cin >> a[i];
        a[i] -= i;
    }
    i64 l = 1, r = n;
    auto check = [&](i64 x)->bool{
        multiset<int,less<>>s2;
        multiset<int,greater<>>s1;
        map<int,int>mp1,mp2;
        i64 sum1 = 0, sum2 = 0;
        for ( int i = 0 ; i < x-1 ; i++ ) {
            s1.insert(a[i]);
            mp1[a[i]]++;
            sum1 += a[i];
            if ( s1.size() > (x+1)/2 ) {
                int t = *s1.begin();
                mp1[t]--;
                mp2[t]++;
                sum1 -= t;
                sum2 += t;
                s2.insert(*s1.begin());
                s1.erase(s1.begin());
            }
        }
        for ( int i = x-1 ; i < n ; i++ ) {
            if ( s1.size() != (x+1)/2 ) {
                int t = *s2.begin();
                if ( a[i] > t ) {
                    sum2 -= t;
                    mp2[t]--;
                    s2.erase(s2.begin());
                    sum2 += a[i];
                    mp2[a[i]]++;
                    s2.insert(a[i]);
                    sum1 += t;
                    mp1[t]++;
                    s1.insert(t);
                } else {
                    sum1 += a[i];
                    mp1[a[i]]++;
                    s1.insert(a[i]);
                }
            } else {
                int t = *s1.begin();
                if ( a[i] < t ) {
                    sum1 -= t;
                    mp1[t]--;
                    s1.erase(s1.begin());
                    sum1 += a[i];
                    mp1[a[i]]++;
                    s1.insert(a[i]);
                    sum2 += t;
                    mp2[t]++;
                    s2.insert(t);
                } else {
                    sum2 += a[i];
                    mp2[a[i]]++;
                    s2.insert(a[i]);
                }
            }
            i64 t = *s1.begin();
            if ( k >= s1.size()*t-sum1+sum2-s2.size()*t ) {
                return 1;
            }
            if ( mp1[a[i-x+1]] ) {
                mp1[a[i-x+1]]--;
                s1.extract(a[i-x+1]);
                sum1 -= a[i-x+1];
            } else {
                mp2[a[i-x+1]]--;
                s2.extract(a[i-x+1]);
                sum2 -= a[i-x+1];
            }
        }
        return 0;

    };
    while ( r > l ) {
        i64 m = (l+r+1)/2;
        if ( check(m) ) {
            l = m;
        } else {
            r = m-1;
        }
    }
    cout << l << '\n';
}
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    int T = 1;
    cin >> T;
    while ( T-- ) {
        solve();
    }
}