View Compilation Error

0_0_21541191_24261.cpp: In function 'int main()':
0_0_21541191_24261.cpp:36:41: error: 'sort' was not declared in this scope
             sort(a+c[i].l-1,a+c[i].r,cmp);
                                         ^
0_0_21541191_24261.cpp:40:22: error: 'strcmp' was not declared in this scope
         if(strcmp(a,b)!=0)
                      ^