foo.cc: In function 'int main()':
foo.cc:19:18: warning: 'sl' may be used uninitialized [-Wmaybe-uninitialized]
   19 |         a[1]=a[sl];
      |              ~~~~^
foo.cc:6:21: note: 'sl' was declared here
    6 |         int n,ans=0,sl;
      |                     ^~