Compilare: user.cpp: In function ‘void solve()’: user.cpp:29:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i < ss1.size();i++) { ~~^~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:65:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("brackets2.in", "r", stdin); ^ user.cpp:66:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("brackets2.out", "w", stdout); ^