COST Verification Competition
Please send solutions to vladimir@cost-ic0701.org

Challenge 3: Two equal elements

Given: An integer array a of length n+2 with n>=2. It is known that at
least two values stored in the array appear twice (i.e., there are at
least two duplets).

Implement and verify a program finding such two values.

You may assume that the array contains values between 0 and n-1.