#include <stdio.h>
#include <stdlib.h>

int main (void) {
    FILE *fin = fopen ("input.bin", "rb");
    FILE *fout = fopen ("output.bin", "wb");

    int x, cur_index = 1, alloc = 2;
    int *a = malloc (2);

    while (fread (&x, sizeof (int), 1, fin)) {
        if (cur_index == alloc) {
            alloc <<= 1;
            a = realloc (a, alloc * sizeof (int));
        }
        a[cur_index] = x;
        ++cur_index;
    }

    int flag1 = 0;

    if (cur_index == 2) {
        x = 0;
        fwrite (&x, sizeof (int), 1, fout);
        return 0;
    }

    for (int i = 1; i < cur_index; ++i) {
        if (i * 2 < cur_index) {
            if (a[i] <= a[i * 2]) {
                flag1 = 1;
            } else {
                flag1 = 0;
                break;
            }
        }
        if (i * 2 + 1 < cur_index) {
            if (a[i] <= a[i * 2 + 1]) {
                flag1 = 1;
            } else {
                flag1 = 0;
                break;
            }
        }
    }

    if (flag1) {
        x = 1;
        fwrite (&x, sizeof (int), 1, fout);
        free (a);
        fclose (fin);
        fclose (fout);
        return 0;
    }

    for (int i = 1; i < cur_index; ++i) {
        if (i * 2 < cur_index) {
            if (a[i] > a[i * 2]) {
                flag1 = 1;
            } else {
                flag1 = 0;
                break;
            }
        }
        if (i * 2 + 1 < cur_index) {
            if (a[i] > a[i * 2 + 1]) {
                flag1 = 1;
            } else {
                flag1 = 0;
                break;
            }
        }
    }

    if (flag1) {
        x = -1;
        fwrite (&x, sizeof (int), 1, fout);
        free (a);
        fclose (fin);
        fclose (fout);
        return 0;
    } else {
        x = 0;
        fwrite (&x, sizeof (int), 1, fout);
    }

    free (a);
    fclose (fin);
    fclose (fout);
    return 0;
}