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;
    vector<int>S(m);
    vector<int>C(m);
    for (int i=0; i<m; i++) cin >> S[i] >> C[i];
    for (int i=0; i<1000; i++){
        string st = to_string(i);
        bool jud = true;
        if (st.size() != n) jud = false;
        for (int j=0; j<m; j++){
            if (st[S[j]-1] != (char)(C[j]+'0')) jud = false;
        }
        if (jud){
            cout << i;
            return 0;
        }
    }
    cout << -1;
}