/in/foo.cc: In function 'int main()':
/in/foo.cc:24:33: warning: iteration 100007 invokes undefined behavior [-Waggressive-loop-optimizations]
         ans = max (ans, num[i][1] - num[i][0]);
                         ~~~~~~~~^
/in/foo.cc:23:23: note: within this loop
     for (int i = 0; i <= 200000; i ++) {
                     ~~^~~~~~~~~