Compilare: user.cpp: In function ‘void mark(int)’: user.cpp:25: warning: unused variable ‘s’ user.cpp: In function ‘int main()’: user.cpp:63: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:64: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:68: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:80: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:83: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result