Compilare: user.cpp: In function ‘void read_input()’: user.cpp:20: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:21: 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 compute()’: user.cpp:49: warning: comparison between signed and unsigned integer expressions user.cpp:56: warning: comparison between signed and unsigned integer expressions user.cpp:57: warning: comparison between signed and unsigned integer expressions user.cpp:68: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void write_output()’: user.cpp:78: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result