View Compilation Error

0_0_25830509_3008.cpp: In function 'void change(int, int)':
0_0_25830509_3008.cpp:21:3: error: 'cout' was not declared in this scope
   cout << "text:"<<tree[k].l <<" "<<tree[k].v<< endl;
   ^
0_0_25830509_3008.cpp:21:49: error: 'endl' was not declared in this scope
   cout << "text:"<<tree[k].l <<" "<<tree[k].v<< endl;
                                                 ^