/in/foo.c: In function 'main':
/in/foo.c:9:17: error: 'Sn' undeclared (first use in this function); did you mean 'n'?
    9 |                 Sn=0,sum=0;
      |                 ^~
      |                 n
/in/foo.c:9:17: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:9:21: warning: left-hand operand of comma expression has no effect [-Wunused-value]
    9 |                 Sn=0,sum=0;
      |                     ^