/in/foo.cc: In function 'int main()':
/in/foo.cc:5:6: warning: unused variable 'i' [-Wunused-variable]
  int i,j,sum=0;
      ^
/in/foo.cc:5:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,sum=0;
        ^
/in/foo.cc:5:10: warning: unused variable 'sum' [-Wunused-variable]
  int i,j,sum=0;
          ^~~