#include <stdio.h>

int main() {
     FILE *fin,*fout;
    fin = fopen("isheap.in","r");
    fout = fopen("isheap.out","w");
    int n;
    fscanf(fin, "%d", &n);
    int A[n];
    for (int i = 1; i<=n; i++) {
        fscanf(fin,"%d", &A[i]);
    }
    int c;
    c=0;
    for (int i = 1; i<=n; i++) {
        if (i + i <= n && A[i]>A[i+i]){
            c = 1;
        }
        if (i + i <= n && A[i]>A[i+i+1]) {
            c = 1;
        }
    }
    if (c==0){
        fprintf(fout,"YES");
    } else {
        fprintf(fout,"NO");
    }
    return 0;
}