View Compilation Error

0_0_27888595_18915.cpp: In function 'int main()':
0_0_27888595_18915.cpp:9:9: error: 'string' was not declared in this scope
         string a,b;        
         ^
0_0_27888595_18915.cpp:10:9: error: 'cin' was not declared in this scope
         cin>>a>>b;
         ^
0_0_27888595_18915.cpp:10:14: error: 'a' was not declared in this scope
         cin>>a>>b;
              ^
0_0_27888595_18915.cpp:10:17: error: 'b' was not declared in this scope
         cin>>a>>b;
                 ^
0_0_27888595_18915.cpp:15:27: error: 'len2' was not declared in this scope
             for(int j=0;j<len2;j++)
                           ^
0_0_27888595_18915.cpp:26:21: error: 'len2' was not declared in this scope
                 i+=(len2-1);            
                     ^
0_0_27888595_18915.cpp:29:9: error: 'cout' was not declared in this scope
         cout<<ans<<endl;
         ^
0_0_27888595_18915.cpp:29:20: error: 'endl' was not declared in this scope
         cout<<ans<<endl;
                    ^