Compilare: user.cpp: In function ‘bool bkt(std::vector<int>)’: user.cpp:17:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i + 1 < c.size();i++) ~~~~~~^~~~~~~~~~ user.cpp:18:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i + 1;j < c.size();j++) { ~~^~~~~~~~~~ user.cpp:21:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int a = 0;a < c.size();a++) ~~^~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:35:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bigfour.in", "r", stdin); ^ user.cpp:36:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bigfour.out", "w", stdout); ^