C++ :

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<vector>
using namespace std;
const int N=100010,M=10010;
int n,m;
int a[N],idx,root[N];
vector<int> nums;
struct Node{
 int l,r;
 int cnt;
}tr[N*4+N*17];
int find(int x){
 return lower_bound(nums.begin(),nums.end(),x)-nums.begin();
}
int build(int l,int r){
 int p=++idx;
 if(l==r)    return p;
 int mid=l+r>>1;
 tr[p].l=build(l,mid),tr[p].r=build(mid+1,r);
 return p;
}
int insert(int p,int l,int r,int x){
 int q=++idx;
 tr[q]=tr[p];
 if(l==r){
  tr[q].cnt++;
  return q;
 }
 int mid=l+r>>1;
 if(x<=mid)   tr[q].l=insert(tr[p].l,l,mid,x);
 else        tr[q].r=insert(tr[p].r,mid+1,r,x);
 tr[q].cnt=tr[tr[q].l].cnt+tr[tr[q].r].cnt;
 return q;
}
int query(int q,int p,int l,int r,int k){
 if(l==r)   return r;
 int cnt=tr[tr[q].l].cnt-tr[tr[p].l].cnt;
 int mid=l+r>>1;
 if(k<=cnt)    return query(tr[q].l,tr[p].l,l,mid,k);
 else          return query(tr[q].r,tr[p].r,mid+1,r,k-cnt);
}
int main(){
 scanf("%d%d",&n,&m);
 for(int i=1;i<=n;i++){
  scanf("%d",&a[i]);
  nums.push_back(a[i]);
 }
 sort(nums.begin(),nums.end());
 nums.erase(unique(nums.begin(),nums.end()),nums.end());
 root[0]=build(0,nums.size()-1);
 for(int i=1;i<=n;i++)
    root[i]=insert(root[i-1],0,nums.size()-1,find(a[i]));
    while(m--){
     int l,r,k;
     scanf("%d%d%d",&l,&r,&k);
     printf("%d\n",nums[query(root[r],root[l-1],0,nums.size()-1,k)]);
    }
    return 0;
}