View Compilation Error

0_0_36458097_6486.cpp: In function 'void tree_change(long long int, long long int, long long int)':
0_0_36458097_6486.cpp:101:26: error: 'x' was not declared in this scope
      long long val = dfn[x] - l;
                          ^
0_0_36458097_6486.cpp:108:26: error: 'y' was not declared in this scope
      long long val = dfn[y] + r;
                          ^