View Compilation Error

0_0_20664237_8235.cpp: In function 'int main()':
0_0_20664237_8235.cpp:6:11: error: 'cin' was not declared in this scope
     while(cin>>n>>a>>b)
           ^
0_0_20664237_8235.cpp:17:25: error: 'printf' was not declared in this scope
       printf("%.2lf\n",l);
                         ^