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>

#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;
const int INF = 1e9;

int main() {
  ll n, m, mxs = 0;
  cin >> n >> m;
  vector<ll> s(m);
  vector<char> c(m);
  rep(i, m) cin >> s[i] >> c[i], s[i]--;

  rep(i, 1000) {
    string S = to_string(i);
    if (S.size() != n) continue;
    bool ok = true;
    rep(j, m) if (S[s[j]] != c[j]) ok = false;
    if (ok) {
      cout << i << endl;
      return 0;
    }
  }

  puts("-1");
  return 0;
}