import math
import statistics


fa = [i for i in range(21)]

def find(i):
    if fa[i] == i:
        return i
    else:
        return find(fa[i])

def hb(i,j):
    i_fa = find(i)
    j_fa = find(j)
    fa[i_fa] = j_fa

m,n = list(map(int,input().split()))

k = int(input())

for i in range(k):
    a,b = list(map(int,input().split()))
    hb(a,b)

count = 0
for i in range(1,len(fa)):
    if fa[i] == i:
        count += 1

print(count)