foo.c: In function 'main':
foo.c:18:11: error: expected ';' before 'while'
   18 |     a[i]=x
      |           ^
      |           ;
   19 |         while(n<=i)
      |         ~~~~~
foo.c:7:17: warning: unused variable 'sum' [-Wunused-variable]
    7 |         int i,n,sum=0;
      |                 ^~~
foo.c:7:15: warning: unused variable 'n' [-Wunused-variable]
    7 |         int i,n,sum=0;
      |               ^
foo.c:5:9: warning: variable 'a' set but not used [-Wunused-but-set-variable]
    5 |     int a[1000];
      |         ^

[Hydro](https://hydro.ac)提供评测服务