c  20. $BG.EAF3J}Dx<0$N(B3$B<!85%0%i%U(B
c     $B?9@n(B $BLwBg(B , 22980138
c
      program ex20
c
      implicit none
      integer :: n0,m0,l0
      real :: u,x,t,n,m,l,pi,tt,xx
c
      u =0.0
      pi=3.141592653589
      do l0=0,50
        l=float(l0)
        t=0.01*l
        do m0=0,20
          m=float(m0)
          x=0.05*m
          u=0.0
          do n0=1,100
             n=float(n0)
             u=u+(8.0/(pi**2))*(1.0/(n**2))*sin((n*pi)/2.0)*
     -         sin(n*pi*x)*exp(-(n**2)*(pi**2)*t)      
          enddo
        tt=0.01*l
        xx=0.05*m
        write(10,*) tt,xx,u
        enddo
      write(10,*)
      enddo      
      
      stop
      end      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
