#include <bits/stdc++.h>
using namespace std;
const int Maxn = int(1e6) + 256;
const int INF = int(1e9) + 7;
struct po {
  int x, y, id;
} t[Maxn];
int n, block = 1000, ix = 1;
vector<po> v;
bool cmp(po a, po b) { return (a.y < b.y); }
bool cmp1(po a, po b) { return (a.x < b.x); }
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(0);
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> t[i].x >> t[i].y;
    t[i].id = i;
  }
  sort(t + 1, t + n + 1, cmp);
  for (int i = 0; i <= 1000; ++i) {
    int l = block * i, r = block * (i + 1);
    while (t[ix].y >= l && t[ix].y < r && ix <= n) {
      v.push_back(t[ix]);
      ix++;
    }
    sort(v.begin(), v.end(), cmp1);
    if (i & 1) {
      reverse(v.begin(), v.end());
    }
    for (auto it : v) cout << it.id << ' ';
    v.clear();
  }
  return 0;
}
