Compilare: user.cpp: In function ‘void add(int)’: user.cpp:10:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[x].size(); ++i) { ^ user.cpp: In function ‘void remove(int)’: user.cpp:20:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[x].size(); ++i) { ^ user.cpp: In function ‘bool query(int)’: user.cpp:31:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[x].size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:42:24: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &n); ^ user.cpp:45:33: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d%d", &op, &x); ^