Compilare: user.cpp: In function ‘int main()’: user.cpp:15:35: warning: for increment expression has no effect [-Wunused-value] for( int j=i*i; j<n; j+i) ~^~ user.cpp:9:34: warning: unused variable ‘j’ [-Wunused-variable] int v[2000001]={0}, i, n, d, j,x=0; ^ user.cpp:15:26: warning: ‘i’ may be used uninitialized in this function [-Wmaybe-uninitialized] for( int j=i*i; j<n; j+i) ^