input:

3
1
111
110110
1101010
1111
111111

output:

-1
15
3 4
6 7
6 7
6 7
7 8
6 7
7 8
4 5
5 6
4 5
5 6
2 3
3 4
2 3
3 4
6
4 5
4 5
5 6
5 6
5 6
6 7

result:

wrong answer (l,r) is invalid (test case 2)