SUBROUTINE OPERATE (ARG, N, ICODE)
    IMPLICIT NONE
    REAL, DIMENSION(:, :) :: ARG
    REAL, DIMENSION(:, :), ALLOCATABLE :: TEMP
    INTEGER :: N, ICODE, I

    IF (N < 0 .OR. UBOUND(ARG, 1) <= 0 .OR. UBOUND(ARG, 2) <= 0 .OR. &
            UBOUND(ARG, 1) /= UBOUND(ARG, 2)) THEN
        ICODE = 1
        RETURN
    END IF
    ALLOCATE(TEMP(UBOUND(ARG, 1), UBOUND(ARG, 2)), STAT=ICODE)
    IF (ICODE /= 0) RETURN
    IF (N == 0) THEN
        ARG = 0.0
        DO I = 1, UBOUND(ARG, 1)
            ARG(I,I) = 1.0
        END DO
    ELSE
        TEMP = ARG
        DO I = 1, N-1
            ARG = MATMUL(ARG,TEMP)
        END DO
    END IF
END SUBROUTINE OPERATE