/in/foo.c: In function 'main':
/in/foo.c:7:16: warning: 'i' is used uninitialized [-Wuninitialized]
    7 |         while(i<=n)
      |               ~^~~
/in/foo.c:5:17: note: 'i' was declared here
    5 |         int a,n,i,sum=0;
      |                 ^