/in/foo.cc: In function 'int main()':
/in/foo.cc:6:10: warning: unused variable 'i' [-Wunused-variable]
  int n,m,i,j;
          ^
/in/foo.cc:6:12: warning: unused variable 'j' [-Wunused-variable]
  int n,m,i,j;
            ^