Compilare: main.cpp: In function 'int main()': main.cpp:22:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < S.size() - 1; ++i, answer = max(answer, length)) { ~~^~~~~~~~~~~~~~ main.cpp:16:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("charlie.in", "r", stdin); ^ main.cpp:17:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("charlie.out", "w", stdout); ^