Compilare: user.cpp: In function ‘int main()’: user.cpp:83:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < v[a].size(); i++){ ^ user.cpp: In function ‘char readch()’: user.cpp:27:26: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(s, BUFF, 1, in); ^