foo.cc: In function ‘int main()’:
foo.cc:5:19: warning: unused variable ‘a’ [-Wunused-variable]
    5 |         int n,i,j,a,b,c;
      |                   ^
foo.cc:5:21: warning: unused variable ‘b’ [-Wunused-variable]
    5 |         int n,i,j,a,b,c;
      |                     ^
foo.cc:5:23: warning: unused variable ‘c’ [-Wunused-variable]
    5 |         int n,i,j,a,b,c;
      |                       ^
foo.cc:8:18: warning: ‘n’ is used uninitialized [-Wuninitialized]
    8 |         for(i=1;i<=n;i++)
      |                 ~^~~
foo.cc:5:13: note: ‘n’ was declared here
    5 |         int n,i,j,a,b,c;
      |             ^