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:26:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i;j<=b;j+=i) ~^~~ main.cpp:34:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i;j<=b;j+=i) ~^~~ main.cpp:15:9: warning: iteration 49998 invokes undefined behavior [-Waggressive-loop-optimizations] if(x[i]==0) ~~~^ main.cpp:13:14: note: within this loop for(int i=2;i<=50000;i++) ~^~~~~~~