Roy is looking for Wobbly Numbers.

An NN-length wobbly number is of the form "ababababab..." and so on of length NN, where a!=ba!=b.

A 3-length wobbly number would be of form "aba".

Eg: 101,121,131,252,646101,121,131,252,646 etc

But 111,222,999111,222,999 etc are not 33-length wobbly number, because here a!=ba!=b condition is not satisfied.

Also 010010 is not a 33-length wobbly number because it has preceding 00. So 010010 equals 1010 and 1010 is not a 33-length wobbly number.

A 44-length wobbly number would be of form "abab".

Eg: 2323,3232,9090,14142323,3232,9090,1414 etc

First 10 terms of 4-length wobbly numbers arranged lexicographically is as follows: 1010,1212,1313,1414,1515,1616,1717,1818,1919,2020

3rd wobbly number of length 4 is 1313. 4th wobbly number of length 4 is 1414.

Similarly 2nd wobbly number of length 5 is 12121

An NN-length wobbly number is of the form "ababababab..." and so on of length NN, where a!=ba!=b.

A 3-length wobbly number would be of form "aba".

Eg: 101,121,131,252,646101,121,131,252,646 etc

But 111,222,999111,222,999 etc are not 33-length wobbly number, because here a!=ba!=b condition is not satisfied.

Also 010010 is not a 33-length wobbly number because it has preceding 00. So 010010 equals 1010 and 1010 is not a 33-length wobbly number.

A 44-length wobbly number would be of form "abab".

Eg: 2323,3232,9090,14142323,3232,9090,1414 etc

Similarly we can form a list of NN-length wobbly numbers.

Now your task is to find KKthth wobbly number from a lexicographically sorted list of NN-length wobbly numbers. If the number does not exist print −1−1 else print the KKtth wobbly number. See the sample test case and explanation for more clarity.

First line contains TT - number of test cases

Each of the next TT lines contains two space separated integers - NN and K

For each test case print the required output in a new line.

6

3 1

3 2

3 100

4 3

4 4

5 2

101

121

-1

1313

1414

12121

First 10 terms of 3-length wobbly numbers arranged lexicographically is as follows: 101,121,131,141,151,161,171,181,191,202

1st wobbly number of length 3 is 101101. 2nd wobbly number of length 3 is 121. 100th wobbly number of length 3 does not exist, so the output is −1−1.

**Input:**First line contains TT - number of test cases

Each of the next TT lines contains two space separated integers - NN and K

**Output:**For each test case print the required output in a new line.

**Sample Input:**6

3 1

3 2

3 100

4 3

4 4

5 2

**Sample Output:**101

121

-1

1313

1414

12121

**Explanation**First 10 terms of 3-length wobbly numbers arranged lexicographically is as follows: 101,121,131,141,151,161,171,181,191,202

1st wobbly number of length 3 is 101101. 2nd wobbly number of length 3 is 121. 100th wobbly number of length 3 does not exist, so the output is −1−1.

First 10 terms of 4-length wobbly numbers arranged lexicographically is as follows: 1010,1212,1313,1414,1515,1616,1717,1818,1919,2020

3rd wobbly number of length 4 is 1313. 4th wobbly number of length 4 is 1414.

Similarly 2nd wobbly number of length 5 is 12121

**Implementation:**

#include <stdio.h> int main() { int t; int n,k,a,b,x,i; scanf("%d",&t); while(t--) { scanf("%d %d",&n,&k); if(k>81) printf("-1\n"); else { a=ceil((double)k/9.0); x=k-9*(a-1); b=x<=a?x-1:x; for(i=0;i<n;i++) { if(!(i&1)) printf("%d",a); else printf("%d",b); } printf("\n"); } } return 0; }