View Compilation Error

0_0_28718696_24776.cpp: In function 'int main()':
0_0_28718696_24776.cpp:6:1: error: 'cin' was not declared in this scope
 cin>>n;
 ^
0_0_28718696_24776.cpp:10:1: error: 'cout' was not declared in this scope
 cout<<a+b<<endl;
 ^
0_0_28718696_24776.cpp:10:12: error: 'endl' was not declared in this scope
 cout<<a+b<<endl;
            ^
0_0_28718696_24776.cpp:11:2: error: 'reyurn' was not declared in this scope
 }reyurn 0;
  ^