Compilare: main.cpp: In function 'int main()': main.cpp:25:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < strlen(s); ++i) ~~^~~~~~~~~~~ main.cpp:16:35: 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:17:37: 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); ^