View Compilation Error

0_0_37368872_21997.cpp: In function 'int main()':
0_0_37368872_21997.cpp:5:34: error: 'scanf' was not declared in this scope
  scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
                                  ^
0_0_37368872_21997.cpp:6:22: error: 'fabs' was not declared in this scope
  a=fabs(x1*x1-(x2*x2));
                      ^
0_0_37368872_21997.cpp:8:12: error: 'sqrt' was not declared in this scope
  m=sqrt(a+b); 
            ^
0_0_37368872_21997.cpp:9:17: error: 'printf' was not declared in this scope
  printf("%.2f",m); 
                 ^