[求助] 崩溃了...不太会使用sum和random函数，所以总是报错

subroutine read_obstacles(obst)
        implicit none
        include "head.inc"
      EXTERNAL sum
      complex h(51,51),h1(51,51),F(51,51),F1(51,51),
     &obst(51,51)
      integer k,l,P,Q
      integer x,y

        do 11 k= 1, 51
                do 10 l = 1, 51
              F(P,Q)=0.675*0.675*(exp(-2.3*((k/50)*(k/50)+(l/10)* 
     &         (l/10))**0.5))*((-1)**(2*k*P/50+2*l*Q/50))
              if (k==(1,51).and.l==(1,51))then
                  F1(P,Q)=sum(F,1,[1:51,1:51])
      end if
   10 continue
   11 continue

      do 20 P=1,51
          do 21 Q=1, 51
              h(k,l)=1/10000*F1(P,Q)*(-1)**((k*P+l*Q)/26)
               if (P==(1,51).and.Q==(1,51))then
               h1(k,l)=sum(h,1,[1:51,1:21])
      end if
   21 continue
   20 continue

      do 22 k= 1, 51
                do 23 l = 1, 51
              call RANDOM_SEED()
              call RANDOM_NUMBER()
              obst(lx,ly)=h1(k,l)*random_number(lx,ly)
              if (lx==(1,51).and.ly==(1,51))then
              obst(x,y)=sum(obst,1,[1:51,1:21])
      end if 
   23 continue
   22 continue

        end