foo.c: In function 'main':
foo.c:5:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    5 |   scanf("%d",&n);
      |   ^~~~~~~~~~~~~~
foo.c:13:13: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   13 |   if(z==1) x=x+i*i;
      |            ~^~~~~~

[Hydro](https://hydro.ac)提供评测服务