Compilare: user.cpp: In function ‘std::vector<int, std::allocator<int> > merge(std::vector<int, std::allocator<int> >, std::vector<int, std::allocator<int> >)’: user.cpp:123: warning: comparison between signed and unsigned integer expressions user.cpp:123: warning: comparison between signed and unsigned integer expressions user.cpp:136: warning: comparison between signed and unsigned integer expressions user.cpp:141: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:163: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result