Найти сумму отрицательный элементов в строках и расположить их по главной диагонали — QBasic(Бейсик)

CLS
INPUT "Kolvo strok="; n
INPUT "Kolvo stolbcov="; m
DIM a(n, m)
RANDOMIZE TIMER
FOR i = 1 TO n
    FOR j = 1 TO m
        a(i, j) = INT(RND * 101) - 50
    NEXT j
NEXT i
PRINT "Ishodniy massiv"
FOR i = 1 TO n
    FOR j = 1 TO m
        PRINT a(i, j);
    NEXT j
    PRINT
NEXT i
FOR i = 1 TO n
    s = 0
    FOR j = 1 TO m
        IF a(i, j) < 0 THEN s = s + a(i, j)
    NEXT j
    IF i <= m THEN a(i, i) = s
NEXT i
PRINT
PRINT "Massiv posle preobrazovaniy"
FOR i = 1 TO n
    FOR j = 1 TO m
        PRINT a(i, j);
    NEXT j
    PRINT
NEXT i