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() {
    ios::sync_with_stdio(0);
    cin.tie(0);

	int n, m;
	cin >> n >> m;
	vector<int> s(m), c(m);
	for(int i=0; i<m; i++) cin >> s[i] >> c[i];

	for(int i=0; i<1000; i++) {
		string x = to_string(i);
		if(x.size() == n) {
			bool valid=1;
			for(int j=0; j<m; j++) {
				if(x[s[j]-1] != ('0' + c[j])) valid=0;	
			}
			if(valid) {
				cout << i;
				return 0;
			}
		}
	}
	cout << -1;
    return 0;
}
