View Compilation Error

0_0_21658972_10797.cpp: In function 'int main()':
0_0_21658972_10797.cpp:75:5: error: 'cin' was not declared in this scope
     cin>>t;
     ^
0_0_21658972_10797.cpp:78:22: error: 'scanf' was not declared in this scope
         scanf("%d",&n);
                      ^
0_0_21658972_10797.cpp:106:29: error: 'printf' was not declared in this scope
         printf("%.2lf\n",ans);
                             ^