-1

I have a data like this:

1 0000100101000000
1 0000010100000000
2 1110000001000000
2 1111000000001000
3 0000000111111111
3 1111111100000000

and I want to sum up the values within eachtwo rows with the same row number: output:

1 0000110201000000
2 2221000001001000
3 1111111211111111

any suggestion please? my real dat had 8000 rows with 45000 digit in each line