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 <iostream>
#include <utility>
#include <string>
#include <vector>
using namespace std;

int main() {
	int n, q;
	cin >> n >> q;
	vector<pair<int, int>> v;
	while(q--) {
		int x, y;
		cin >> x >> y;
		v.push_back({x, y});
	}
	for(int i = 0; i <= 1000; ++i) {
		string s = to_string(i);
		if((int)s.size() == n) {
			bool ok = true;
			for(pair<int, int> x : v) {
				if(s[x.first - 1] - '0' != x.second) {
					ok = false;
					break;
				}
			}
			if(ok)
				return cout << i, 0;
		}
	}
	cout << -1;
}
