push elements into the stack
st . push ( '1' ) NEW_LINE st . push ( '2' ) NEW_LINE st . push ( '3' ) NEW_LINE st . push ( '4' ) NEW_LINE st . push ( '5' ) NEW_LINE st . push ( '6' ) NEW_LINE st . push ( '7' ) NEW_LINE deleteMid ( st , st . size ( ) , 0 ) NEW_LINE