Compilare: main.cpp: In function 'void convex_hull()': main.cpp:46:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0;i < v.size();++i) { ~~^~~~~~~~~~ main.cpp:65:34: warning: format '%i' expects argument of type 'int', but argument 3 has type 'std::vector<int>::size_type {aka long unsigned int}' [-Wformat=] fprintf(fout,"%i\n", poly.size()); ^ main.cpp: In function 'int main()': main.cpp:77:23: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%i", &n); ^ main.cpp:80:31: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%f %f", &x, &y); ^