#include <bits/stdc++.h>

using namespace std;

typedef long long llint;
typedef pair <int, int> pii;

#define TRACE(x) cerr << #x << ' ' << x << endl
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define REP(i, n) FOR(i, 0, n)
#define _ << ' ' <<

#define X first
#define Y second

const int MAXN = 100100;
const int offset = (1 << 18);

struct node {
	int x, y, val, prop;
	int last_val;
	int set;

	node(){
		last_val = 1;
		prop = set = 0;
		val = 0;
	}
};

struct tournament {
	node p[offset * 2];

	node merge(node a, node b, int last) {
		node ret;
		ret.last_val = last;
		if (!b.set) ret = a;
		if (!a.set) ret = b;
		if (!b.set || !a.set) ret.last_val = last;
		if (!b.set || !a.set) return ret;
		ret.set = 1;
		ret.x = min(a.x, b.x);
		ret.y = max(a.y, b.y);
		ret.val = last * (b.x - a.y - 1) + a.val + b.val;
		return ret;
	}

	void postavi(int x, int real_x) {
		x += offset;
		p[x].x = p[x].y = real_x;
		p[x].set = 1;
		p[x].val = p[x].last_val = 1;
		x /= 2;
		while (x) {
			p[x] = merge(p[x * 2], p[x * 2 + 1], p[x].last_val);
			x /= 2;
		}
	}

	void send_prop(int x) {
		if (!p[x].prop) return;
		FOR(i, x * 2, x * 2 + 2) {
			p[i].val = p[i].y - p[i].x + 1 - p[i].val;
			p[i].prop ^= 1;
			p[i].last_val ^= 1;
		}
		p[x].prop = 0;
	}

	void update(int cvor, int l, int r, int a, int b) {
		if (l > b || r < a) return;
		if (l >= a && r <= b) {
			p[cvor].val = p[cvor].y - p[cvor].x + 1 - p[cvor].val;
			p[cvor].prop ^= 1;
			p[cvor].last_val ^= 1;
			return;
		}

		send_prop(cvor);

		int mid = (l + r) / 2;
		update(cvor * 2, l, mid, a, b);
		update(cvor * 2 + 1, mid + 1, r, a, b);
		p[cvor] = merge(p[cvor * 2], p[cvor * 2 + 1], p[cvor].last_val);
	}

	int get() {
		return p[1].val;
	}

	void print() {
		FOR(i, 1, 2 * offset) TRACE(p[i].last_val _ p[i].val _ p[i].prop _ p[i].x _ p[i].y _ p[i].set);
	}
}T;

int m, n, k;
int a, b, c, d;

vector <int> v;

vector <pair <pii, pii> > ev;

int get(int t) {
	return (int)(lower_bound(v.begin(), v.end(), t) - v.begin());
}

int main() {
	scanf("%d %d %d",&n,&m,&k);
	REP(i, k) {
		scanf("%d %d %d %d",&a,&b,&c,&d);
		v.push_back(c);
		v.push_back(d);
		ev.push_back({{a, -1}, {c, d}});
		ev.push_back({{b, 1}, {c, d}});
	}
	v.push_back(1);
	v.push_back(m);
	sort(v.begin(), v.end());
	sort(ev.begin(), ev.end());

	v.erase(unique(v.begin(), v.end()), v.end());
	REP(i, (int)v.size()) T.postavi(i, v[i]);

	int last = ev[0].X.X;
	llint sol = 0;
	REP(i, (int)ev.size()) {
		int x = ev[i].X.X;
		vector <pii> add, rem;
		for (int j = i; j < (int)ev.size() && ev[j].X.X == ev[i].X.X; j++) {
			if (ev[j].X.Y == -1) add.push_back({get(ev[j].Y.X), get(ev[j].Y.Y)});
			else rem.push_back({get(ev[j].Y.X), get(ev[j].Y.Y)});
		}
		int prije = T.get();
		sol += (llint)prije * (x - last);
		if (x == n && add.empty()) sol += prije;
		REP(j, (int)add.size()) T.update(1, 0, offset - 1, add[j].X, add[j].Y);
		last = x;
		if (!add.empty()) {
			last++;
			sol += T.get();
		}
		REP(j, (int)rem.size()) T.update(1, 0, offset - 1, rem[j].X, rem[j].Y);
		while (i < (int)ev.size() && ev[i].X.X == x) i++;
		i--;
	}

	printf("%lld\n", sol);

	return 0;
}