/in/foo.c: In function 'main':
/in/foo.c:5:17: error: 'sum' undeclared (first use in this function); did you mean 'sun'?
    5 |                 sum=0;
      |                 ^~~
      |                 sun
/in/foo.c:5:17: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:3:17: warning: unused variable 'sun' [-Wunused-variable]
    3 |         int n,i,sun=0;
      |                 ^~~