Compilare: user.cpp: In function ‘std::pair<int, int> backtrack(int, int, int, int, std::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > >)’: user.cpp:43: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:67: 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 ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:73: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:75: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result