def main():
    import sys
    input = sys.stdin.readline
    W = int(input())
    H = int(input())
    N = int(input())
    SK = [list(map(int,input().split())) for _ in range(N)]
    count = W+H-2
    count *= N
    
    for i in range(N):
        for j in range(i+1,N):
            if SK[i][0] == SK[j][0]:
                count -= W
            elif SK[i][1] == SK[j][1]:
                count -= H
            else:
                count -= 2
    print(count)

if __name__ == '__main__':
    main()