View Compilation Error

0_0_17236563_21136.cpp: In function 'void add(int, int, int)':
0_0_17236563_21136.cpp:28:66: error: 'upper_bound' was not declared in this scope
     r = upper_bound(pos[ mmp[x] ].begin(), pos[ mmp[x] ].end(), r) - pos[ mmp[x] ].begin() - 1;
                                                                  ^