Compilare: main.cpp: In function 'int nr(int)': main.cpp:33:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int nr, i = 0; i * i < x && i < primes.size(); ++i) { ~~^~~~~~~~~~~~~~~ main.cpp: In function 'std::vector<std::pair<int, int> > decomp_into_prime_factors(int)': main.cpp:49:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int nr, i = 0; i * i < x && i < primes.size(); ++i) { ~~^~~~~~~~~~~~~~~ main.cpp: In function 'std::pair<int, int> find_numbers(std::vector<std::pair<int, int> >&)': main.cpp:80:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < prime_factors.size(); ++j) { ~~^~~~~~~~~~~~~~~~~~~~~~