/in/foo.cc: In function 'int main()':
/in/foo.cc:7:33: warning: 'n' is used uninitialized [-Wuninitialized]
    7 |         for(long double i=1;i<=2*n-1;i+=2)
      |                                ~^~
/in/foo.cc:5:19: note: 'n' was declared here
    5 |         long long n;
      |                   ^