problem . why i m getting wrong answer ~~~~~ ` ~~~~~ Your code here... ~~~~~

#include<iostream> 
  #include<cmath>
      #include<utility>
   #include<cstdio>
   using namespace std;
      int N=50000;
      int M[1<<23][2];
     int a[1<<23];
        void initialize(int node,int i,int j)
      {
          if(i==j)
        {
              if(a[i]>0)
              M[node][0]=a[i];
             else
        M[node][0]=0;
        M[node][1]=a[i];
     }
        else
       {       
        initialize(2*node,i,(i+j)/2);
         initialize(2*node+1,(i+j)/2+1,j);
         M[node][0]=M[2*node][0]+M[2*node+1][0];
          M[node][1]=M[2*node][1]>M[2*node+1][1]?M[2*node][1]:M[2*node+1][1];
          }
        }
        pair<int,int> query(int node,int b,int e,int i,int j)
          {
            pair<int,int>  p1,p2;
             if(i>e||j<b)
         return make_pair(0,-15008);
          if(b>=i&&e<=j)
     return make_pair(M[node][0],M[node][1]);
           p1=query(2*node,b,(b+e)/2,i,j);
        p2=query(2*node+1,(b+e)/2+1,e,i,j);  
            return make_pair(p1.first+p2.first,max(p1.second,p2.second));

         }
         int main()
            {
           pair<int,int> AL; 
          int m,n;
              cin>>n;
           for(int i=0;i<n;i++)
           cin>>a[i];
             initialize(1,0,n-1);
            cin>>m;
            int x,y;
            while(m--)
        {
           cin>>x>>y;
          AL=query(1,0,n-1,x-1,y-1);
        if(AL.first==0)
            cout<<AL.second<<endl;
        else
    cout<<AL.first<<endl;

    }

          }