View Compilation Error

0_0_20567729_12003.cpp: In function 'int main()':
0_0_20567729_12003.cpp:15:14: error: 'max' was not declared in this scope
   a=max(x1,x3);
              ^
0_0_20567729_12003.cpp:16:14: error: 'min' was not declared in this scope
   c=min(x2,x4);
              ^