If you gets WA#17 may be you assume that first string of each blog is "<blog>" but it only begins with "<blog>".
I only changed in my program "readln(s);" to "for i:=1 to 6 do read(c)" and got AC.

I had WA17 but my mistake was:
On one string could be several frend's tags, also there could be </blog>(on the same string)...