/in/foo.cc: In function 'void add_sum(int, int)':
/in/foo.cc:28:7: warning: statement has no effect [-Wunused-value]
  for(x;x<=n;x+=lowbit(x)) t[x]+=y;
       ^
/in/foo.cc: In function 'int query(int)':
/in/foo.cc:33:7: warning: statement has no effect [-Wunused-value]
  for(x;x>=1;x-=lowbit(x)) all+=t[x];
       ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:48:3: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   if(l>r) swap(l,r);if(k>w) swap(k,w);
   ^~
/in/foo.cc:48:21: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
   if(l>r) swap(l,r);if(k>w) swap(k,w);
                     ^~