If there is an integer not less than 0 satisfying the following conditions, print the smallest such integer; otherwise, print `-1`.

* The integer has exactly N digits in base ten. (We assume 0 to be a 1-digit integer. For other integers, leading zeros are not allowed.)
* The s_i-th digit from the left is c_i. \left(i = 1, 2, \cdots, M\right)

Constraints

* All values in input are integers.
* 1 \leq N \leq 3
* 0 \leq M \leq 5
* 1 \leq s_i \leq N
* 0 \leq c_i \leq 9

Input

Input is given from Standard Input in the following format:


N M
s_1 c_1
\vdots
s_M c_M


Output

Print the answer.

Examples

Input

3 3
1 7
3 2
1 7


Output

702


Input

3 2
2 1
2 3


Output

-1


Input

3 1
1 0


Output

-1
#include <bits/stdc++.h>
using namespace std;

int main() {
  int N, M; cin >> N >> M;
  int s[5], c[5]; for (int i = 0; i < M; i++) {cin >> s[i] >> c[i]; s[i]--;}

  for (int i = 0; i <= 999; i++) {
    string x = to_string(i);

    if (x.size() != N) {
      continue;
    }

    bool ok = true;
    for (int j = 0; j < M; j++) {
      if (x[s[j]] != (char)(c[j] + '0')) {
        ok = false;
        break;
      }
    }

    if (ok) {
      cout << x << endl;
      return 0;
    }
  }

  cout << -1 << endl;
  return 0;
}