Jerry and Tom are playing a game on a directed graph (G) with (n) vertices, numbered from (1) to (n). For every vertex (1 \le u < n), there is a directed edge from (u) to (u+1). In addition, there are (m) extra directed edges. The (i)-th extra edge goes from (u_i) to (v_i), where (1 \le u_i < v_i \le n). The graph (G) has the following special property: there do not exist two directed edges ((u_i\to v_i)) and ((u_j\to v_j)) such that (u_i < u_j < v_i < v_j). At the beginning of the game, Jerry and Tom stand on vertices (x) and (y), respectively, where (x \ne y). The game proceeds in turns. In each turn, the players behave according to the following rules, with Jerry going first, followed by Tom: Jerry must choose one outgoing edge from his current vertex and move along it to its end. If his current vertex has no outgoing edges, he stays where he is. Tom may choose one outgoing edge from his current vertex and move along it to its end, or choose not to move and stay where he is. If at the end of any turn, Jerry and Tom are at the same vertex ( including at vertex (n) ), the game ends immediately and Tom wins. Otherwise, if Jerry is initially at vertex (n), or reaches vertex (n) at the end of any turn, Jerry wins. Note that if after a turn, both Jerry and Tom are at vertex (n), then Tom wins . Throughout the entire game, both players know each others' locations. It can be proven that the game will end in a finite number of turns. For a pair of integers (1 \le x,y \le n), (x \ne y), define (f(x,y)) as follows: Jerry and Tom will play a game, where Jerry starts at vertex (x) and Tom starts at vertex (y). Tom wants to win, but he also wants to minimise the number of times he actually moves (that is, the number of turns in which he changes his vertex; staying still does not count as a move ). Assuming both players play optimally, let (f(x,y)=0) if