Compilare: main.cpp: In function 'int main()': main.cpp:54:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (s . size () < n){ ~~~~~~~~~~~~^~~ main.cpp: In function 'bool nextc()': main.cpp:30:45: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread (buff , 1 , (1 << 14) , stdin); ^ main.cpp: In function 'int main()': main.cpp:42:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("domino.in" , "r" , stdin); ^ main.cpp:44:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d" , &n); ^ main.cpp:47:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d" , &a , &b); ^