View Compilation Error

0_0_35411784_2099.cpp: In function 'int main()':
0_0_35411784_2099.cpp:4:48: error: 'scanf' was not declared in this scope
     while(~scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2)){
                                                ^
0_0_35411784_2099.cpp:5:63: error: 'sqrt' was not declared in this scope
         s = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
                                                               ^
0_0_35411784_2099.cpp:6:27: error: 'printf' was not declared in this scope
         printf("%.2lf\n",s);
                           ^