Finding the Big and Exact Match of Sample Data

Hi all,

I am comparatively to new to excel programming and in urgent need of some help....
I have data in two columns and i need to find the exact and big match of values in column A from that in Column B in new column C.

A B C(Required Results)
7890 8900 7890
7891 7890 Not Found
894 7909 89
8058 89 Not Found
8059 792 Not Found


Kindly suggest any way via programming or using build-in excel formulas for the resolution of the issue.

Thanks