%{
#include <stdio.h>
#include <stdlib.h>

void yyerror(const char *s);
int yylex();
%}

%token NUMBER
%token PLUS MINUS MULTIPLY DIVIDE
%token LPAREN RPAREN

%%
input:
    | input line
    ;

line:
    '\n'
    | expr '\n' { printf("Result: %d\n", $1); }
    ;

expr:
    term
    | expr PLUS term   { $$ = $1 + $3; }
    | expr MINUS term  { $$ = $1 - $3; }
    ;

term:
    factor
    | term MULTIPLY factor  { $$ = $1 * $3; }
    | term DIVIDE factor    { if ($3 == 0) yyerror("Division by zero"); else $$ = $1 / $3; }
    ;

factor:
    NUMBER
    | LPAREN expr RPAREN { $$ = $2; }
    ;

%%

void yyerror(const char *s) {
    fprintf(stderr, "Error: %s\n", s);
}

int main() {
    printf("Enter expressions:\n");
    return yyparse();
}