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

%% 
program:
program expr '\n' {printf("%d\n",$2);}
|
;
expr:
INTEGER {$$ = $1;}
|  expr '+' expr {$$ = $1 + $2;}
| expr '-' expr {$$ = $1 -$2;}
;
%%
void yyerror(char *S)
{
fprintf(stderr,"%s\n",S);
}