main()
{
	char op[2];
	int i1, i2;

	while(1) {
		printf("Enter expression: ");
		if (scanf("%d %s %d", &i1, op, &i2) == EOF)
			break;
	
		push(i1);
		push(i2);

		if (op[0] == '+')
			add();
		else if (op[0] == '-')
			subtract();
		else if (op[0] == '*')
			multiply();
		else if (op[0] == '/')
			divide();
		else {
			fprintf(stderr, "Unknown operator >%s<\n", op);
			pop();		/* discard both operands */
			pop();
			push(0);	/* substitute a zero result */
		}
		
		printf("Result = %d\n", pop());
	}

	return 0;
}