i have a document written in MS Word 2003 and the structure of the document is as

this is a line number 1_p1

this is a line number 2_p1

this is a line number 3_p1

this is a line number 4_p1

this is a line number 1_p2

this is a line number 2_p2

this is a line number 3_p2

this is a line number 4_p2

this is a line number 1_p3

this is a line number 2_p3

this is a line number 3_p3

this is a line number 4_p3

now here i want to display these information as

p1

this is a line number 1

this is a line number 2

this is a line number 3

this is a line number 4

p2

this is a line number 1

this is a line number 2

this is a line number 3

this is a line number 4

p3

this is a line number 1

this is a line number 2

this is a line number 3

this is a line number 4

here please note that every line consist of symbol `_`

as separator.