#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) {a = max(a, b);}
template<class T> void chmin(T& a, const T& b) {a = min(a, b);}
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m, q;
    cin >> n >> m >> q;
    VI cnt1(n), cnt2(m);
    VI to1(n, -1), to2(m, -1);
    rep(_, q) {
        int a, b;
        cin >> a >> b;
        cnt1[a - 1]++;
        cnt2[b - 1]++;
        to1[a - 1] = b - 1;
        to2[b - 1] = a - 1;
    }
    constexpr int INF = 1001001001;
    VI dp(m + 1, -INF);
    dp[0] = 0;
    rep(i, n) {
        VI ndp(m + 1, -INF);
        if (cnt1[i] == 1 && cnt2[to1[i]] == 1) {
            int x = -INF;
            rep(j, to1[i] + 1) chmax(x, dp[j]);
            chmax(ndp[to1[i] + 1], x + 1);
        }
        if (cnt1[i] == 0) {
            int x = -INF;
            rep(j, m) chmax(x, dp[j]), chmax(ndp[j + 1], x + 1);
        } else {
            int x = -INF;
            rep(j, m) if (cnt2[j] == 0) chmax(x, dp[j]), chmax(ndp[j + 1], x + 1);
        }
        rep(i, m + 1) chmax(ndp[i], dp[i]);
        dp = ndp;
    }
    int ans = *max_element(all(dp));
    cout << ans << endl;
}