Compilare: user.cpp: In function ‘int main()’: user.cpp:47:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < primes.size() ; ++i) ^ user.cpp:60:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < primes.size() ; ++i) ^ user.cpp:71:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < primes.size() ; ++i) ^