View Compilation Error

0_0_16224139_23992.cpp: In function 'int main()':
0_0_16224139_23992.cpp:26:38: error: 'fabs' was not declared in this scope
         if(sum<0)sum=0,liqi+=fabs(sum);
                                      ^
0_0_16224139_23992.cpp:30:42: error: 'fabs' was not declared in this scope
             if(sum<0)sum=0,liqi+=fabs(sum);
                                          ^