#include<iostream>
#include<algorithm>
#include<string.h>
#include<vector>
#include<set>
using namespace std;
// #define debug(x) cout<<"[debug]"#x<<"="<<x<<endl
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
const ld eps=1e-8;
const int INF=0x3f3f3f3f,mod=998244353;
const ll INFF=0x3f3f3f3f3f3f3f3f;

#ifndef ONLINE_JUDGE
#define debug(...)
#include<debug>
#else
#define debug(...)
#endif

const int N=500005;
int a[N];
ll k;
int n;
void solve()
{
    scanf("%d%lld",&n,&k);
    for(int i=1;i<=n;i++) scanf("%d",&a[i]),a[i]-=i;
    vector<multiset<int>> S(2);

    int res=1;
    ll now=0;//操作的次数
    int mid=-1;
    vector<ll> sum(2);
    auto ins=[&](int t,int x){
        S[t].insert(x);
        sum[t]+=x;
    };
    auto era=[&](int t,int x){
        S[t].erase(S[t].find(x));
        sum[t]-=x;
    };
    auto update=[&](){
        if(S[0].empty()&&S[1].empty()) return ;
        while(S[0].size()<S[1].size())
        {
            auto x=*S[1].begin();
            ins(0,x);
            era(1,x);
        }
        while(S[0].size()>S[1].size()+1)
        {
            auto x=*S[0].rbegin();
            era(0,x);
            ins(1,x);
        }
        mid=*S[0].rbegin();
        now=(1ll*S[0].size()*mid-sum[0])+(sum[1]-1ll*S[1].size()*mid);
    };
    for(int l=1,r=0;l<=n;l++)
    {
        while(now<=k&&r<=n)
        {
            r++;
            if(r==n+1) break;
            if(a[r]<=mid||S[0].empty()) ins(0,a[r]);
            else ins(1,a[r]);
            update();
        }
        res=max(res,r-l);
        if(a[l]<=mid) era(0,a[l]);
        else era(1,a[l]);
        update();
    }
    printf("%d\n",res);
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        solve();
    }
}