#include <bits/stdc++.h>
using namespace std;
int n, m, c1[6], s1[4];
string s, c = "02345";
map<int, int> mp;
bool b;
int main() {
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    cin >> s1[i] >> c1[i];
    mp[s1[i]]++;
  }
  for (int i = 0; i < m; i++) {
    if (mp[s1[i]] > 1) b = 1;
  }
  for (int i = 0; i < m; i++) {
    c[s1[i]] = c1[i];
  }
  if (c[0] == '0' || b == 1)
    cout << "-1" << endl;
  else {
    for (int i = 0; i < n; i++) cout << c[i] << endl;
  }
}
