foo.cc: In function ‘int main()’:
foo.cc:14:17: error: ‘c’ was not declared in this scope
   14 |                 c=a+b,
      |                 ^
foo.cc:17:17: error: ‘d’ was not declared in this scope
   17 |                 d+=c;
      |                 ^
foo.cc:18:15: error: ‘d’ was not declared in this scope
   18 |         cout<<d<<endl;
      |               ^
foo.cc:6:23: warning: unused variable ‘c，d’ [-Wunused-variable]
    6 |         int n,a=1,b=1,c，d;
      |                       ^~~~