// strings starting with atleast 5 'a's followed by any number of 'a's and ending with 'b'
%{ 
	int yylex();
	#include<stdio.h>
	void yyerror(char *s){
		printf("%s\n",s);
	}
%} 
%token A B NL 
%% 
stmt: A A A A A S B NL	{
									printf("valid string\n"); 
									exit(0);
								}
S: S A 
|     
%%
void main(){
	yyparse();
}