#include <bits/stdc++.h>
int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int n, m;
  std::cin >> n >> m;
  std::vector<int> l(m + 1);
  std::vector<int> r(m + 1);
  std::vector<int> k(m + 1);
  std::vector<int> v(m + 1);
  std::vector<int> ans(n, -1);
  int ok = 1;
  for(int i = 1; i <= m; i++) {
    std::cin >> l[i] >> r[i] >> k[i] >> v[i];
    assert(k[i] == 1);
    for(int j = l[i]; j <= r[i]; j++) {
      if(ans[j] != - 1) {
        ok = 0;
      }
      ans[j] = v[i];
    }
  }
  if(!ok) {
    std::cout << - 1;
    return 0;
  }
  for(int i = 0; i < n; i++) {
    if(ans[i] == - 1) {
      ans[i] = 0;
    }
    std::cout << ans[i] << " "[i == n - 1];
  }
}
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