BEGIN

REQUIRE "IODEFS.SAI[SEC,RCP]" SOURCE_FILE;

SAFE STRING ARRAY OPNAM[0:3];
INTEGER OP;
STRING LINE;

OPNAM[0] ← "Add";
OPNAM[1] ← "Subtract";
OPNAM[2] ← "Multiply";
OPNAM[3] ← "Divide";

OP ← 0;

WHILE (LINE ← GET_A_STRING(OPNAM[OP])) DO
	IF LINE = "A" THEN OP ← 0
	ELSE IF LINE = "S" THEN OP ← 1
	ELSE IF LINE = "M" THEN OP ← 2
	ELSE IF LINE = "D" THEN OP ← 3
	ELSE IF LINE > "9" THEN OUTSTR("What's that again ?" ↓)
	ELSE	BEGIN
		INTEGER SUM;
		CASE OP OF
		BEGIN
	BEGIN
	SUM ← 0;
	DO SUM ← SUM + INTSCAN(LINE, BRK) UNTIL BRK = -1;
	END;
	SUM ← INTSCAN(LINE, BRK) - INTSCAN(LINE, BRK);
	SUM ← INTSCAN(LINE, BRK) * INTSCAN(LINE, BRK);
	BEGIN
	INTEGER DIVIDEND, DIVISOR;
	DIVIDEND ← INTSCAN(LINE, BRK);
	DIVISOR ← INTSCAN(LINE, BRK);
	OUTSTR(CVS(DIVIDEND DIV DIVISOR) ∂ " r ");
	SUM ← DIVIDEND MOD DIVISOR;
	END;
		END;
		OUTSTR((CVS(SUM)) ↓);
		END;
END