Compilare: user.cpp: In function ‘void df(int, int)’: user.cpp:16:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:55:29: warning: unused variable ‘x’ [-Wunused-variable] for (int j = 1, x; j <= M; j++) { ^ user.cpp:44:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("verlab.in", "r", stdin); ^ user.cpp:45:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("verlab.out", "w", stdout); ^