/in/foo.cc:11:30: warning: '-std=c++11' is not an option that controls warnings [-Wpragmas]
 #pragma GCC diagnostic error "-std=c++11"
                              ^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:63:10: warning: unused variable 't' [-Wunused-variable]
  int n,m,t,a,l=0;
          ^