DECLARE FUNCTION NOD! (a!, b!)

CLS
INPUT "A,B,C = "; a, b, c
PRINT NOD(NOD(a, b), c)
END

FUNCTION NOD (a, b)
   IF a = 0 OR b = 0 THEN
      NOD = a + b
   ELSE
      IF a > b THEN
         NOD = NOD(a MOD b, b)
      ELSE
         NOD = NOD(a, b MOD a)
      END IF
   END IF
END FUNCTION