1

//
//  main.cpp
//  qwerty
//
//  Created by Святой Отец on 11.09.17.
//  Copyright © 2017 Святой Отец. All rights reserved.
//

#include <fstream>
#include <iostream>
#include <cmath>


using namespace std;

bool IsHeap=true;
int lenght=NULL;

void hueta(int* heap,int index){
    if(IsHeap){
    if(2*index+1<lenght)
        if(heap[index]>=heap[2*index+1])
                IsHeap=false;
            else
                hueta(heap,2*index+1);
    else;
    if(2*index+2<lenght)
        if(heap[index]>=heap[2*index+2])
            IsHeap=false;
        else
            hueta(heap,2*index+2);
        else;
    }
}

int main(int argc, const char * argv[]) {
    ifstream fin("/Users/i9788365/Desktop/qwerty/qwerty/1.rtf");
    fin>>lenght;
    int * heap = (int*) malloc(lenght + 1);
    for(int i=0;i<lenght;i++)
        cin>>heap[i];
    int a;
    fin>>a;
    cout<<a<<lenght;
    fin.close();
    ofstream fout("isheap.out");
    hueta(heap,0);
    cout<<(IsHeap?"YES":"NO");
    fout.close();
    free(heap);
}