#include <iostream>
#include <vector>

using namespace std;

int main(){
	int a, b, n;
	vector<int> record;
	int count = 0;
	int judge = 0;
	cin >> a;
	cin >> b;
	cin >> n;

	int c[n];

	for(int i = 0; i < n; i++){
		cin >> c[i];
	}

	record[0] = c[0];
	for(int i = 0; i < n; i++){
		for(int j = 0; j < record.size(); j++){
			if(c[i] == record[j]){
				count++;
			}else{
				judge++;
			}
		}
		if(judge != record.size()){
			record.push_back(c[i]);
		}
		judge = 0;
	}

	cout << (a + b) * (count - 1) / 2 << endl;
	return 0;
}