Compilare: user.cpp: In function ‘int main()’: user.cpp:71:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0;j < V[el].size();j++) { ^ user.cpp: In function ‘char next()’: user.cpp:27:35: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buf, 1, BUF, fin), pos = 0; ^