program fall_polt

      write(*,*)'initial position ?'
      read(*,*)x
      xini=x
      write(*,*)'initial hight ?'
      read(*,*)y
      write(*,*)'Vx ?'
      read(*,*)vx
      write(*,*)'Vy ?'
      read(*,*)vy

      if(pgopen('/xwin')<=0)stop
      call pgenv(0.0,10.0,0.0,10.0,1,0)

      dt=0.0001
      do while(y>0)
        ax=0.0
        ay=-9.8
        vx=vx+ax*dt
        vy=vy+ay*dt
        x=x+vx*dt
        y=y+vy*dt
        call pgpt(1,x,y,20)
      end do

      write(*,*)'Final hight =',y,'meters.'
      write(*,*)'Final distace =',x-xini,'meters.'

      call pgclos

      end