%{
int yylex();
void yyerror (char *s);
#include <stdio.h>
#include <stdlib.h>
%}

%start calculation
%token NUMBER
%token IDENTIFIER

%%

calculation: expression '\n' {printf("=%d\n", $1); return 0;};
			;
expression: expression '+' NUMBER	{$$ = $1 + $3;}
       	| expression '-' NUMBER		{$$ = $1 - $3;}
       	| expression '*' NUMBER		{$$ = $1 * $3;}
       	| expression '/' NUMBER		{$$ = $1 / $3;}
	| NUMBER
%%


int main (void) {
	return yyparse();
}

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