program RMSposition

    implicit none
    real,dimension(2000)::y
    character(len=20)::pr1
    real::sumy
    integer::i

    open(UNIT = 1, FILE = "positions", ACTION = "read", position = "ASIS")
    
    do i=1,19
        read(1,*)
    end do

    do i=1,2000
        read(1,*),pr1,y(i)
    end do

    sumy=0
    do i=1,2000
        sumy=sumy+((y(i)-0.5)**2)
    end do
    sumy=sqrt(sumy/2000)
    
    write(*,*),' RMS Displacement = ',sumy
    read(*,*)

    end