Compilare: main.cpp: In function 'int main()': main.cpp:76:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < str.length(); i += 2) { ~~^~~~~~~~~~~~~~ main.cpp:57:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sqrt.in", "r", stdin); ^ main.cpp:58:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sqrt.out", "w", stdout); ^