Compilare: main.cpp: In function 'int main()': main.cpp:64:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ciclueuler.in", "r", stdin); ^ main.cpp:65:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ciclueuler.out", "w", stdout); ^ main.cpp: In function 'char next()': main.cpp:12:39: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buffer, 1, BUFFER_SIZE, stdin); ^