Compilare: user.cpp: In function ‘void make_hulls()’: user.cpp:23:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < pts[0].size(); ++i) { ^ user.cpp:28:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < pts[1].size(); ++i) { ^ user.cpp: In function ‘void get_calipers()’: user.cpp:34:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(p0 = p1 = 0; p1 + 1 < hull[1].size(); ++p1) { ^ user.cpp:35:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; p0 < hull[0].size() && ccw(hull[1][p1], hull[1][p1 + 1], hull[0][p0]) <= 0; ++p0); ^ user.cpp:36:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(p0 == hull[0].size()) ^ user.cpp:39:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(p0 = 0; p0 + 1 < hull[0].size(); ++p0) ^ user.cpp: In function ‘int main()’: user.cpp:44:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("oypara.in", "r", stdin); ^ user.cpp:45:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("oypara.out", "w", stdout); ^ user.cpp:47:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:52:66: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &pts[0][i].x, &pts[0][i].y, &pts[1][i].y); ^