Compilare: user.c: In function ‘main’: user.c:12:11: warning: unused variable ‘nr’ [-Wunused-variable] int N,j,n,nr,i,a[2000010]; ^ user.c:12:9: warning: unused variable ‘n’ [-Wunused-variable] int N,j,n,nr,i,a[2000010]; ^ user.c:18:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fp,"%d",&N); ^ user.c:29:6: warning: ‘r’ may be used uninitialized in this function [-Wmaybe-uninitialized] r=r*2; ^