PROGRAM vct
    IMPLICIT NONE
      INTEGER, ALLOCATABLE, DIMENSION(:) :: mgs
      INTEGER, ALLOCATABLE, DIMENSION(:) :: xps
      INTEGER, ALLOCATABLE, DIMENSION(:) :: yps
      REAL    :: fx
      REAL    :: fy
      INTEGER :: i
      INTEGER :: j
      INTEGER :: k
      INTEGER :: n
      REAL(3), PARAMETER :: pi = 3.1415926536
      REAL(3), PARAMETER :: e0 = 8.854187817e-12

!      CHARACTER (LEN=1) :: m1

  fx = 0
  fy = 0
  i  = 0

  WRITE(6,*) 'How many charges?'
  READ(5,* )  n

  ALLOCATE(mgs(n))
  ALLOCATE(xps(n))
  ALLOCATE(yps(n))

  DO
    IF (i /= n) THEN
      i=1+i
      WRITE(6,*) 'Enter magnitude of charge number',i
      READ(5,* ) mgs(i)
      WRITE(6,*) 'Enter x-position of this charge (between -10 and 10)'
      READ(5,* ) xps(i)
      WRITE(6,*) 'Enter y-position of this charge (between -10 and 10)'
      READ(5,* ) yps(i)
      CYCLE
    ELSE
      EXIT
    END IF
  END DO

  DO i=-10,10,1
    DO j=-10,10,1
      DO k=1,SIZE(mgs),1
        IF ((ABS(xps(k)-i) /= 0) .AND. (ABS(yps(k)-j) /= 0)) THEN
          fx = fx + (mgs(k)*(xps(k)-i))/(4*pi*e0*(ABS(xps(k)-i))**3)
          CYCLE
        ELSE
          CYCLE
        END IF
      END DO

      DO k=1,SIZE(mgs),1
        IF ((ABS(xps(k)-i) /= 0) .AND. (ABS(yps(k)-j) /= 0)) THEN
          fy = fy + (mgs(k)*(yps(k)-j))/(4*pi*e0*(ABS(yps(k)-j))**3)
          CYCLE
        ELSE
          CYCLE
        END IF
      END DO
      WRITE(6,*) i, j, fx, fy
    END DO
  END DO
  DEALLOCATE(mgs(n))
  DEALLOCATE(xps(n))
  DEALLOCATE(yps(n))
END PROGRAM vct