Compilare: user.cpp: In function ‘void get_calipers()’: user.cpp:32:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0, j = 0; i < hull[0].size() - 1 && j < hull[1].size(); ++i) ^ user.cpp:32:66: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0, j = 0; i < hull[0].size() - 1 && j < hull[1].size(); ++i) ^ user.cpp:33:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; j + 1 < hull[1].size() && ccw(hull[0][i], hull[0][i + 1], hull[1][j]) > 0; ++j); ^ user.cpp: In function ‘int main()’: user.cpp:39:38: 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:40:39: 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:42:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:47:66: 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); ^