Shell Programming and Scripting

Input file:

Code:

1234 USA date
3421 USA date
3421 USA content
1234 USA1 date
34 USA1 content
1234 USA2 Sun
34 USA2 Sun
43 USA2 Sun
345 USA2 date
435 USA2 date1

Output file:

Code:

1234 USA date
3421 USA date
1234 USA1 date
1234 USA2 Sun
34 USA2 Sun
43 USA2 Sun
345 USA2 date

If the consecutive line that share second and share third column are exactly the same, keep whole content that share exactly second and third column;
If the consecutive line that share second but don't share third column are different, keep only the first appear record;

Thanks for any advice.