foo.cc: In function 'int main()':
foo.cc:7:19: warning: left operand of comma operator has no effect [-Wunused-value]
    7 |         for(i=1;;i<n-1,i++)
      |                  ~^~~~
foo.cc:16:34: warning: 's' may be used uninitialized [-Wmaybe-uninitialized]
   16 |                                 s+=i;
      |                                 ~^~~
foo.cc:5:13: note: 's' was declared here
    5 |         int s,n,i;
      |             ^