（国王放置）在n*m的棋盘上放置k个国王，要求k个国王互相不攻击，有多少种不同的放置方法。假设国王放置在第(x, y)格，国王的攻击的区域是：(x-1,y-1), (x-1,y), (x-1,y+1), (x, y-1), (x,y+1), (x+1,y-1), (x+1,y), (x+1,y+1)。读入三个数n,m,k，输出答案。题目利用回溯法求解。棋盘行标号为0~n-1，列标号为0~m-1。

var    n, m, k, ans: integer; 
   hash: array[0..4, 0..4] of integer;
procedure work(x, y, tot: integer);
var    i, j: integer;
begin
    if tot = k then  begin
        inc(ans);  exit;
    end;
    repeat
        while hash[x, y] <> 0 do  begin
            inc(y);
            if y = m then   begin
                inc(x);    y :=    0   ;
            end;
            if x = n then   exit;
        end;
        for i := x - 1 to x + 1 do
            if (i >= 0) and (i < n) then
                for j := y - 1 to y + 1 do
                    if (j >= 0) and (j <= m) then
       inc(hash[i,j])      ;
      work(x,y,tot+1)      ;
        for i := x - 1 to x + 1 do
            if (i >= 0) and (i < n) then
                for j := y - 1 to y + 1 do
                    if (j >= 0) and (j <= m) then        dec(hash[i,j])      ;
        inc(y);
        if y = m then  begin
            inc(x);  y := 0;
   end;
        if x = n then   exit;
    until false;
end;
begin
    read(n, m, k);    ans := 0;
    fillchar(hash, sizeof(hash), 0);
          work(0,0,0)      ;
    writeln(ans);
end.