View Compilation Error

0_0_30325575_20289.cpp: In function 'void dfs(int, int, int, int)':
0_0_30325575_20289.cpp:11:8: error: 'cout' was not declared in this scope
        cout<<b[0];
        ^
0_0_30325575_20289.cpp:15:14: error: 'endl' was not declared in this scope
        cout<<endl;
              ^
0_0_30325575_20289.cpp: In function 'int main()':
0_0_30325575_20289.cpp:25:12: error: 'cin' was not declared in this scope
     while((cin>>n>>len)&&len){
            ^
0_0_30325575_20289.cpp:27:25: error: 'sort' was not declared in this scope
         sort(a,a+len,cmp);
                         ^
0_0_30325575_20289.cpp:28:9: error: 'cout' was not declared in this scope
         cout<<"Sums of "<<n<<":"<<endl;
         ^
0_0_30325575_20289.cpp:28:35: error: 'endl' was not declared in this scope
         cout<<"Sums of "<<n<<":"<<endl;
                                   ^