Compilare: user.cpp: In function ‘void read()’: user.cpp:18: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void solve()’: user.cpp:36: warning: comparison between signed and unsigned integer expressions user.cpp:72: warning: unused variable ‘v’ user.cpp: In function ‘void write()’: user.cpp:82: warning: comparison between signed and unsigned integer expressions