Compilare: user.cpp: In function ‘void read()’: user.cpp:17: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void init()’: user.cpp:61: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void solve()’: user.cpp:84: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void write()’: user.cpp:99: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result