Compilare: user.cpp: In function ‘int main()’: user.cpp:26:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < C.size(); i++) F[i + 1] = C[i] - '0'; ^ user.cpp:30:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < word.size(); j++) ^ user.cpp:49:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = 0; k < word.size(); k++) nr = nr * 10 + word[k] - '0'; ^