Compilare: user.cpp: In function ‘int main()’: user.cpp:29:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j < a.length(); ++j) { ^ user.cpp:43:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j < b.length(); ++j) { ^ user.cpp:15:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("joben.in", "r", stdin); ^ user.cpp:16:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("joben.out", "w", stdout); ^ user.cpp:20:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^