Sum of two matrices in FORTRAN

Method. Read the order (rows R, columns C), then read both matrices with a nested implied DO (the inner variable J varies fastest, so the data is entered row by row). The two matrices must have the same order. Add corresponding elements in nested DO loops and display the sum, one row per line.

      PROGRAM MATSUM
      INTEGER A(10,10), B(10,10), S(10,10)
      INTEGER R, C, I, J
      PRINT *, 'ENTER NUMBER OF ROWS AND COLUMNS'
      READ *, R, C
      PRINT *, 'ENTER ELEMENTS OF FIRST MATRIX'
      READ *, ((A(I,J), J = 1, C), I = 1, R)
      PRINT *, 'ENTER ELEMENTS OF SECOND MATRIX'
      READ *, ((B(I,J), J = 1, C), I = 1, R)
      DO 20 I = 1, R
         DO 10 J = 1, C
            S(I,J) = A(I,J) + B(I,J)
   10    CONTINUE
   20 CONTINUE
      PRINT *, 'SUM OF THE TWO MATRICES'
      DO 30 I = 1, R
         WRITE(*,100) (S(I,J), J = 1, C)
   30 CONTINUE
  100 FORMAT(10I6)
      STOP
      END

Sample: A = [1 2 3; 4 5 6], B = [6 5 4; 3 2 1] gives

     7     7     7
     7     7     7