Compilare: user.cpp: In function ‘int main()’: user.cpp:21:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(x>M) ^ user.cpp:26:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=2;i<=M;i++) ^ user.cpp:31:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=2;j<=M/i;++j) ^ user.cpp:41:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=2;i<=M;++i) ^ user.cpp:46:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=1;j<=M/i;j++) ^