Compilare: user.cpp: In function ‘int main()’: user.cpp:20:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i <= strlen(s1) - 1; i++) ^ user.cpp:12:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sr.in", "r", stdin); ^ user.cpp:13:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sr.out", "w", stdout); ^