Compilare: user.cpp: In function ‘int main()’: user.cpp:26:6: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s[lg]=NULL; ^ user.cpp:22:25: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d%d",&m,&n); ^ user.cpp:23:15: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(s,2,fin); ^ user.cpp:24:20: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(s,600000,fin); ^