Compilare: main.cpp: In function 'int main()': main.cpp:20:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=2;i<=b&&i*i<=b;i++) ~^~~ main.cpp:25:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i;j<=b;j+=i) ~^~~ main.cpp:32:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i;j<=b;j+=i) ~^~~