Compilare: main.cpp: In function 'int main()': main.cpp:11:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<strlen(a); i++) ~^~~~~~~~~~ main.cpp:6:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("text.in", "r", stdin); ^ main.cpp:7:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("text.out", "w", stdout); ^