I have multiple entries in a file which look like this. 
1HDZ-B    3NT5-A    0.489917    0.400067
1I30-B    2B35-E    0.879363    0.400068
1K0U-E    1UWK-A    0.969722    0.400072
1BPW-A    1EFL-C    0.556795    0.400077
1EFL-C    1BPW-A    0.556795    0.400077
1GIQ-B    3QJ5-B    0.997880    0.400077
1GEE-A    2B4R-O    0.829231    0.400080

[download]

for the 4th and 5th line,the first two columns are interchanged, i.e.1st column on line4 =2nd column on the subsequent line. so what if i want to keep only one line among lines 4 and 5. say the line 4, so that my file looks like this: 

1HDZ-B    3NT5-A    0.489917    0.400067
1I30-B    2B35-E    0.879363    0.400068
1K0U-E    1UWK-A    0.969722    0.400072
1BPW-A    1EFL-C    0.556795    0.400077
1GIQ-B    3QJ5-B    0.997880    0.400077
1GEE-A    2B4R-O    0.829231    0.400080

[download]

also, there are multiple instances of this occurrence in my file. so how do i remove such redundant entries?

In reply to removing redundant entries by anasuya

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