I'm comparing two large datasets containing strings in excel. Column A contains the numbers 1-1,000,000. Column B contains 1,000,000 strings, neatly organized in the desired order. Column C contains 100,000 randomly organized strings, that have identical values somewhere in column B.

Example:

```
A B C D
1 String1 String642
2 String2 String11
3 String3 String8000
4 String4 String78
```

What I'd like to do is find duplicate values in columns B and C then output the Column A value that corresponds with the string in Column C into Column D.

Desired Output:

```
A B C D
1 String1 String642 642
2 String2 String11 11
3 String3 String8000 8000
4 String4 String78 78
```