#include<bits/stdc++.h>
#define ll long long
#define ssz(x) ((int)x.size())
using namespace std;
const int N=5e5+5;
int n;
ll K,A[N];
inline int red(){
	int data=0;bool w=0;char ch=getchar();
	while(ch!='-' && (ch<'0' || ch>'9'))ch=getchar();
	if(ch=='-') w=1,ch=getchar();
	while(ch>='0' && ch<='9') data=(data<<3)+(data<<1)+ch-'0',ch=getchar();
	return w?-data:data;
}
map <int,int> cnt;
set <int> S;
ll calcNeed(ll sumx,ll x,ll sumz,ll z,ll midval){
	return midval*x-sumx+sumz-midval*z;
}
void solve(){
	scanf("%d%lld",&n,&K);
	cnt.clear();
	S.clear();
	for(int i=1;i<=n;i++){
		scanf("%lld",&A[i]);
		A[i]-=i;
	}
	int l=1,r=0,ans=1,flag=1;
	ll sumx=0,x=0,y=0,yval=0,sumz=0,z=0;
//	ll sumy=0;
	while(flag){
		flag=0;
		while(r<n&&calcNeed(sumx,x,sumz,z,yval)<=K){
			if(l<=r)ans=max(ans,r-l+1);
			flag=1;
			r++;
			if(A[r]==yval){
//				sumy+=A[r];
				++y;
			}else if(A[r]<yval){
				sumx+=A[r];
				x++;
			}else{
				sumz+=A[r];
				z++;
			}
			S.insert(A[r]);
			cnt[A[r]]+=1;
			if(z>x+y){
				sumx+=y*yval;
				x+=y;
				auto now=S.find(yval);
				++now;
				yval=*now;
				y=cnt[yval];
				sumz-=y*yval;
				z-=y;
			}
			if(x>y+z){
				sumz+=y*yval;
				z+=y;
				auto now=S.find(yval);
				--now;
				yval=*now;
				y=cnt[yval];
				sumx-=y*yval;
				x-=y;
			}
			if(l<=r&&calcNeed(sumx,x,sumz,z,yval)<=K){
				ans=max(ans,r-l+1);
			}
		}
		while(calcNeed(sumx,x,sumz,z,yval)>K&&l<=r){
			if(A[l]==yval){
//				sumy-=yval;
				--y;
			}else if(A[l]<yval){
				sumx-=A[l];
				x--;
			}else{
				sumz-=A[l];
				z--;
			}
			--cnt[A[l]];
			if(cnt[A[l]]==0){
				S.erase(A[l]);
			}
			if(z>x+y){
				sumx+=y*yval;
				x+=y;
				auto now=S.find(yval);
				++now;
				yval=*now;
				y=cnt[yval];
				sumz-=y*yval;
				z-=y;
			}
			if(x>y+z){
				sumz+=y*yval;
				z+=y;
				auto now=S.find(yval);
				--now;
				yval=*now;
				y=cnt[yval];
				sumx-=y*yval;
				x-=y;
			}
			flag=1;
			l++;
		}
	}
	printf("%d\n",ans);
}
int main()
{
	//ios::sync_with_stdio(false);
	//cin.tie(0);
	//cout.tie(0); 
	int T=1;
	T=red();
	while(T--)solve();
	return 0;
}
/*
  12
  7 5
  7 2 5 5 4 11 7
  6 0
  100 3 4 5 99 100
  5 6
  1 1 1 1 1
  5 50
  100 200 300 400 500
  1 100
  3
  7 2
  2 3 3 4 5 6 7
  7 1
  2 3 3 4 5 6 7
  7 0
  2 3 3 4 5 6 7
 */