/in/foo.cc: In function 'void dfs(int, int, int)':
/in/foo.cc:19:14: error: 'abs' was not declared in this scope
  if (abs(ex-x)+abs(ey-y)>(t-k+1)) return;
              ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:46:16: error: 'abs' was not declared in this scope
   if ((abs(ex-1)+abs(ey-1))%2!=t%2)
                ^
/in/foo.cc:56:10: error: expected '}' at end of input
  return 0;
          ^