Compilare: user.cpp: In function ‘void read()’: user.cpp:20: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:24: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void solve()’: user.cpp:38: warning: comparison between signed and unsigned integer expressions user.cpp:74: warning: unused variable ‘v’ user.cpp: In function ‘void write()’: user.cpp:83: warning: comparison between signed and unsigned integer expressions