Compilare: user.cpp: In function ‘bool solve(std::vector<std::vector<int> >&, std::vector<int>&)’: user.cpp:37:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(unsigned i = 1; i <= N; i++) { ^ user.cpp: In function ‘int main()’: user.cpp:67:33: warning: format ‘%ld’ expects argument of type ‘long int’, but argument 3 has type ‘std::vector<int>::size_type {aka unsigned int}’ [-Wformat=] fprintf(out, "%ld\n", S.size()); ^ user.cpp:54:29: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d %d", &N, &M); ^ user.cpp:60:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d %d", &x, &y); ^