Compilare: main.cpp: In function 'void ciur()': main.cpp:32:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 4; i < isPrime.size(); i += 2) isPrime[i] = false; ~~^~~~~~~~~~~~~~~~ main.cpp:33:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 3; i < isPrime.size(); i += 2) { ~~^~~~~~~~~~~~~~~~ main.cpp:36:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 3 * i; j < isPrime.size(); j += 2 * i) isPrime[j] = false; ~~^~~~~~~~~~~~~~~~