Compilare: user.cpp: In function ‘bool prim(long long unsigned int)’: user.cpp:34:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; 1LL * prime[i] * prime[i] <= x; ++i) ^ user.cpp: In function ‘void backtr(long long unsigned int, int)’: user.cpp:44:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pos == lg+1) ^ user.cpp:46:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < lg; ++i) ^