Compilare: user.cpp: In function ‘int main()’: user.cpp:41:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < r.size(); ++i) { ^ user.cpp:61:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); ++i) { ^ user.cpp:20:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("pipe.in", "r", stdin); ^ user.cpp:21:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("pipe.out", "w", stdout); ^ user.cpp:25:46: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d%d", &N, &xi, &yi, &xf, &yf); ^ user.cpp:30:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &length); ^