Compilare: user.cpp: In function ‘void convex_hull()’: user.cpp:44:12: warning: unused variable ‘p’ [-Wunused-variable] int i, p, Head; ^ user.cpp: In function ‘void Convex_hull()’: user.cpp:62:12: warning: unused variable ‘p’ [-Wunused-variable] int i, p, Head; ^ user.cpp: In function ‘void read()’: user.cpp:81:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("rubarba.in", "r", stdin); ^ user.cpp:82:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:84:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &v[i].x, &v[i].y); ^ user.cpp: In function ‘void write()’: user.cpp:137:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("rubarba.out", "w", stdout); ^ user.cpp: In function ‘void solve()’: user.cpp:88:20: warning: ‘p3’ may be used uninitialized in this function [-Wmaybe-uninitialized] int i, p1, p2, p3; ^