Hi, Thank you for your answer, but this wasn't the problem. I dont want to find just the minima and maxima of a chromosome. I want to find the overlapping regions and find the minima and maxima of that. So when there are lines in the 4 files like this:

file1:
chr1    100    500
chr1    25      50
file2:
chr1    10       50
chr1    60       80
file3:
chr1    12       40
chr1    41       45
file4:
chr1     20      45
chr1     48      80
[download]

The line of the first file does not overlap with the other 3 files, so i dont want to find the minima and maxima. I want to find only the minima and maxima of the regions in which the lines of all four files overlap each other. So the minima and maxima of the other regions in the files. Minima = 10 maxima = 80

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