Compilare: user.cpp: In function ‘int key(std::vector<int, std::allocator<int> >&)’: user.cpp:25: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘bool check(std::vector<int, std::allocator<int> >&)’: user.cpp:32: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:79: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, 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:81: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:84: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:86: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result