/in/foo.cc: In function 'int main()':
/in/foo.cc:8:31: warning: array subscript is above array bounds [-Warray-bounds]
  for(;x<=n;x+=lowbit(x)) sum[k][x]++;
                          ~~~~~^
/in/foo.cc:8:31: warning: array subscript is above array bounds [-Warray-bounds]
/in/foo.cc:13:33: warning: array subscript is above array bounds [-Warray-bounds]
  for(;x;x-=lowbit(x)) ans+=sum[k][x];
                            ~~~~~^