foo.cc: In function 'int main()':
foo.cc:11:27: warning: 's' may be used uninitialized [-Wmaybe-uninitialized]
   11 |                         (s+=i);
      |                         ~~^~~~
foo.cc:4:23: note: 's' was declared here
    4 |         long long i,n,s;
      |                       ^