Найти все отрицательные элементы матрицы и выбрать наибольший (исправить код)

CLS
INPUT n, m
DIM a(n, m)
FOR i = 1 TO n
FOR j = 1 TO m
NEXT
NEXT
Mi = 1
Mj = 1
Ma = 1
FOR i = 1 TO n
FOR j = 1 TO m
IF a >= 0 THEN GOTO 1
IF a > Ma THEN Ma = a: Mi = i: Mj = j
1 NEXT j
NEXT i
PRINT Mi, Mj, Ma
END

CLS
 INPUT "strok:", m
 INPUT "stolbcov:", n
 
DIM A(n, m), Opr, MaxInMin, Mx, My
 
  ' Generiruem maricu
  RANDOMIZE TIMER
  FOR iy = 1 TO m: FOR ix = 1 TO n
   A(ix, iy) = INT(RND * 101) - 50
   PRINT A(ix, iy);
  NEXT: PRINT : NEXT
 
  ' Poisk
  FOR iy = 1 TO m: FOR ix = 1 TO n
    IF A(ix, iy) < 0 THEN
       IF Opr = 0 THEN
        MaxInMin = A(ix, iy): Mx = ix: My = iy: Opr = 1
       ELSE :
        IF A(ix, iy) > MaxInMin THEN MaxInMin = A(ix, iy): Mx = ix: My = iy
       END IF
    END IF
  NEXT: NEXT
 
  ' Vivod rezultata
  IF Opr = 1 THEN
   PRINT "Znacheniye:"; MaxInMin
   PRINT "Stroka"; My
   PRINT "Stolbec"; Mx
  ELSE
   PRINT "Netu ni odnogo otricatelnogo elementa"
  END IF