Compilare: user.cpp: In function ‘int pref(std::string, std::string)’: user.cpp:21:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (min>B.length()) ^ user.cpp: In function ‘int main()’: user.cpp:33:24: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d",&N); ^ user.cpp:35:27: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%s",S); ^