Compilare: user.cpp: In function ‘int main()’: user.cpp:52:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=1;j<X[i].size();j++) ^ user.cpp: In function ‘char nextch()’: user.cpp:20:30: 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,MAXBUF,fi); ^