I've just learnt range minimum and maximum queries using segment trees.But when I implemented it on my own I'm getting wrong answer.Logically I don't find any mistake in my code but if any one can point it out then I would be really thankful.

Code in C++:

#include<bits/stdc++.h>
using namespace std;
#define LL long long
#define mp make_pair
#define pb push_back
#define gc getchar_unlocked
#define pc putchar_unlocked
#define LD long double
#define MAXN 19999999
#define max(a,b) ((a)>(b)?(a):(b))
LL P[MAXN+15];
LL ST[2*MAXN+25];
long N,M,i,A,B,K;

void build(long id,long L,long R)
{
    long M=(L+R)>>1L;
    long LCT=id<<1L;
    long RCT=LCT+1L;
    if(L==R)
    {
    ST[id]=P[L];
    return;
    } 
    build(LCT,L,M);
    build(RCT,M+1,R);
}


//Range Update of segment tree
void updateST(long id,long L,long R,long Q1,long Q2,long val)
{
    long M=(L+R)>>1L;
    long LCT=id<<1L;
    long RCT=LCT+1L;
    if(L>Q2||R<Q1)
    {
    return;
    }
    if(L==Q1&&R==Q2)
    {
    ST[id]+=val;
    return;
        }
    if(Q2<=M)
    {
        updateST(LCT,L,M,Q1,Q2,val);
    }
    else if(Q1>M)
    {
        updateST(RCT,M+1,R,Q1,Q2,val);
    }
    else
    {
        updateST(LCT,L,M,Q1,M,val);
        updateST(RCT,M+1,R,M+1,Q2,val);
    }
}
//Query for finding maximum element in a given range[Q1,Q2] and 1<=Q1,Q2<=N
LL query2(long id,long L,long R,long Q1,long Q2)
{
  long M=(L+R)>>1;
  long LCT=id<<1;
  long RCT=LCT+1;
   if(L>Q2||R<Q1)
   {
        return 0;
   }
   if(L==Q1&&R==Q2)
   {
        return ST[id];
    }
     if(Q2<=M)
     {
          return query2(LCT,L,M,Q1,Q2);
     }
    else if(Q1>M)
    {
        return query2(RCT,M+1,R,Q1,Q2);
    }
    else
    {
        LL G=query2(LCT,L,M,Q1,M);
        LL H=query2(RCT,M+1,R,M+1,Q2);
        LL RES=max(G,H);
        return RES;
    }

   }

   int main()
   {
    scanf("%ld %ld",&N,&M);
    build(1,1,N);
    for(i=0;i<M;i++)
    {
        scanf("%ld %ld %ld",&A,&B,&K);
        updateST(1,1,N,A,B,K);
    }
        //Finding maximum element in range[1,N]]
    cout<<query2(1,1,N,1,N);
    return 0;
   }