View Compilation Error

0_0_16504036_21105.cpp: In function 'int main()':
0_0_16504036_21105.cpp:31:2: error: 'cin' was not declared in this scope
  cin>>t;
  ^
0_0_16504036_21105.cpp:46:9: error: 'cout' was not declared in this scope
         cout<<sum<<endl;
         ^
0_0_16504036_21105.cpp:46:20: error: 'endl' was not declared in this scope
         cout<<sum<<endl;
                    ^