#pragma GCC optimize("Ofast")
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <string>
#include <map>
#include <queue>
#include <bitset>
#include <vector>
#include <stack>
#include <cmath>
#include <set>
#include <cassert>
#include <random>
#include <chrono>
#include <ctime>
#include <cstdlib>
#define pii pair<int,int> 
#define mp make_pair
#define pb emplace_back
#define debug() cout<<"qwq"<<endl
typedef long long ll;
typedef double db;
typedef long double ldb;
typedef unsigned long long ull;
const int DMAX = 500000 + 5;
const double INF = 1e9;
const int MOD = 998244353;
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
template<class T> inline void read(T &x){
    T f=1; x=0; char ch=getchar();
    while(ch<'0' || ch>'9'){
        if(ch=='-') f=-1; 
        ch=getchar();
    }
    while(ch<='9' && ch>='0'){ x=x*10+ch-'0';ch=getchar(); }
    x*=f;
}
int T;
int n;
ll k;
int a[DMAX], b[DMAX];
multiset<int> s1, s2;
int siz1, siz2;
ll sum1, sum2;
void balance(){
    while(siz1 < siz2){
        int x = *s2.begin();
        s1.insert(x);
        s2.erase(s2.begin());
        siz1 ++, siz2 --;
        sum1 += b[x], sum2 -= b[x];
    }
    while(siz1 > siz2 + 1){
        auto it = s1.end();
        it --;
        int x = *it;
        s1.erase(it), s2.insert(x);
        siz1 --, siz2 ++;
        sum1 -= b[x], sum2 += b[x];
    }
}
bool check(int v){
    s1.clear(), s2.clear();
    siz1 = siz2 = 0;
    sum1 = sum2 = 0;
    for(int i = 1; i <= v; i++){
        if(!siz1) s1.insert(a[i]), siz1 ++, sum1 += b[a[i]];
        else{
            int x = *s1.rbegin();
            if(a[i] <= x) s1.insert(a[i]), siz1 ++, sum1 += b[a[i]];
            else s2.insert(a[i]), siz2 ++, sum2 += b[a[i]];
            balance();
        }
    }
    int x = *s1.rbegin();
    ll temp = 1ll * siz1 * b[x] - sum1 + sum2 - 1ll * siz2 * b[x];
    // cout<<x<<" ";
    // cout<<temp<<endl;
    if(temp <= k) return 1;
    for(int i = v + 1; i <= n; i++){
        int x = *s1.rbegin();
        if(a[i - v] <= x) s1.erase(s1.find(a[i -v])), siz1 --, sum1 -= b[a[i - v]];
        else s2.erase(s2.find(a[i - v])), siz2 --, sum2 -= b[a[i - v]];
        balance();
        if(!siz1){
            s1.insert(a[i]), siz1 ++, sum1 += b[a[i]];
            balance();
        }
        else{
            x = *s1.rbegin();
            if(a[i] <= x) s1.insert(a[i]), siz1 ++, sum1 += b[a[i]];
            else s2.insert(a[i]), siz2 ++, sum2 += b[a[i]];
            balance();
        }
        x = *s1.rbegin();
        temp = 1ll * siz1 * b[x] - sum1 + sum2 - 1ll * siz2 * b[x];
        // cout<<x<<" ";
        // cout<<temp<<endl;
        if(temp <= k) return 1;
    }
    return 0;
}
void solve(){
    read(n), read(k);
    for(int i = 1; i <= n; i++){
        read(a[i]);
        a[i] -= i;
        b[i] = a[i];
    }
    sort(b + 1, b + n + 1);
    int len = unique(b + 1, b + n + 1) - b - 1;
    for(int i = 1; i <= n; i++){
        a[i] = lower_bound(b + 1, b + len + 1, a[i]) - b;
    }

    int l = 2, r = n + 1, res = 1;

    // cout<<check(3)<<endl;
    // return ;
    while(l < r){
        int mid = (l + r) >> 1;
        if(check(mid)){
            res = mid, l = mid + 1;
        }
        else r = mid;
    }
    printf("%d\n", res);
    return ;
}
int main(){
    read(T);
    while(T--){
        solve();
    }
    return 0;
}