Compilare: main.cpp: In function 'void fill_primes(std::vector<int>&)': main.cpp:12:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 3; i < PRIME_LIMIT; i+=2) ~~^~~~~~~~~~~~~ main.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 3; j*i < PRIME_LIMIT; j+=2) ~~~~^~~~~~~~~~~~~ main.cpp: In function 'int magic(int, int, const std::vector<int>&)': main.cpp:32:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (found < k && i < primes.size()) ~~^~~~~~~~~~~~~~~ main.cpp:31:15: warning: 'last' may be used uninitialized in this function [-Wmaybe-uninitialized] int found=0, last, i=0; ^~~~