Retina, 44 25 bytes
+`'([^']).(.*).(.)
$1$2$3
Assumes input in following format (in unary - counting character: '):
{number of repeats}{string}
For example: '''''''ABCDEFGHIJKLMNOP
There is no space between number of repeats and the string.
Thanks @MartinBüttner for shaving off 19 bytes!