foo.cc: In function 'void write(ll, char)':
foo.cc:26:13: warning: array subscript has type 'char' [-Wchar-subscripts]
     do a[++s]=x%10|48;while(x/=10);
             ^
foo.cc:27:19: warning: array subscript has type 'char' [-Wchar-subscripts]
     do putchar(a[s]);while(--s);
                   ^
foo.cc: In function 'void add(int, int, ll)':
foo.cc:43:12: warning: operation on 'l' may be undefined [-Wsequence-point]
         a[l>>=1]=max(a[l],a[l^1])+b[l>>1];
           ~^~~~
foo.cc:43:12: warning: operation on 'l' may be undefined [-Wsequence-point]
foo.cc:44:12: warning: operation on 'r' may be undefined [-Wsequence-point]
         a[r>>=1]=max(a[r],a[r^1])+b[r>>1];
           ~^~~~
foo.cc:44:12: warning: operation on 'r' may be undefined [-Wsequence-point]

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