/in/foo.c: In function 'main':
/in/foo.c:5:13: warning: 'a' is used uninitialized [-Wuninitialized]
    5 |         int Sn=a,b=0;
      |             ^~
/in/foo.c:4:9: note: 'a' declared here
    4 |     int a,n,i;
      |         ^