subsequence.cpp: In function 'int main()':
subsequence.cpp:15:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen ("subsequence.in", "r", stdin);
                                        ^
subsequence.cpp:16:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen ("subsequence.out", "w", stdout);
                                          ^
subsequence.cpp:18:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf ("%d", &n);
                  ^
subsequence.cpp:21:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d", a + i);;
                      ^
subsequence.cpp:23:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d", b + i);
                      ^