Define a word to be a string of characters, none of which are spaces, surrounded by spaces. For example, the string "this sentence has five words" has five words.

We will say a word is a function if and only if:

1. The first character is any character. We say this first character denotes the function, or is the denoting character.

2. The second character is "(", and only one "(" appears in the word.

3. The last character is ")", and only one ")" appears in the word.

4. A polynomial expression appears between the "(" and the ")".

Over all functions that appear in the problem statements of all 12 questions on the USAJMO and USAMO, what will be the most common denoting character?

(The character is case sensitive.)