【codevs1907】方格取数3（最大流最小割定理）

var a:array[0..1010,0..1010]of longint;
  s:array[0..50,0..50]of longint;
  l,q:array[0..1010]of longint;
  n,m,nn,i,j,k,h,t:longint;
  ans,sum:int64;
function num(x,y:longint):longint;
begin
  exit((x-1)*m+y);
end;
function dfs(now,ll:longint):longint;
var p,i:longint;
begin
  if now=nn then exit(ll);
  for i:=1 to nn do
    if(a[now,i]>0)and(l[i]=l[now]+1)then begin
      if a[now,i]<ll then p:=dfs(i,a[now,i])
      else p:=dfs(i,ll);
      a[now,i]:=a[now,i]-p; a[i,now]:=a[i,now]+p;
      if p>0 then exit(p);
    end;
  exit(0);
end;
begin
  read(n,m); sum:=0;
  for i:=1 to n do
    for j:=1 to m do begin
      read(s[i,j]);
      sum:=sum+s[i,j];
    end;
  fillchar(a,sizeof(a),0);
  for i:=1 to n do
    for j:=1 to m do
      if (i+j)and 1=0 then a[num(i,j),n*m+1]:=s[i,j]
      else begin
        if i>1 then a[num(i,j),num(i-1,j)]:=1<<25;
        if i<n then a[num(i,j),num(i+1,j)]:=1<<25;
        if j>1 then a[num(i,j),num(i,j-1)]:=1<<25;
        if j<m then a[num(i,j),num(i,j+1)]:=1<<25;
        a[0,num(i,j)]:=s[i,j];
      end;
  nn:=n*m+1; ans:=0;
  while true do begin
    fillchar(l,sizeof(l),0);
    h:=1; t:=1; q[1]:=0; l[0]:=1;
    repeat
      for i:=1 to nn do
        if(a[q[h],i]>0)and(l[i]=0)then begin
          inc(t); q[t]:=i; l[i]:=l[q[h]]+1;
        end;
      inc(h);
    until h>t;
    if l[nn]=0 then break;
    repeat
      k:=dfs(0,1<<25);
      ans:=ans+k;
    until k=0;
  end;
  writeln(sum-ans);
end.