// Matching paranthesis with error message and continue
%{ 
	int yylex();
	#include<stdio.h>
	void yyerror(char *s){
		printf("%s\n",s);
	}
%} 
%%
Lines	:  Lines S '\n'	{ printf("OK \n"); }
		|  S '\n'
		|  error '\n'		{
      							yyerror("re-enter last line..");
      							yyerrok; 
      						};
S		:  '(' S ')'
		|   
%%
void main(){
	yyparse();
}