Compilare: user.cpp: In function ‘void solve()’: user.cpp:12:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < w.length(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:24:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fences.in", "r", stdin); ^ user.cpp:25:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fences.out", "w", stdout); ^