Compilare: user.cpp: In function ‘void open_files()’: user.cpp:15: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:16: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp: In function ‘void read()’: user.cpp:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘int search(unsigned int)’: user.cpp:56: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘long long int solve_subseq(int)’: user.cpp:66: warning: left shift count >= width of type