#include<bits/stdc++.h>
#define ll long long
#define pll pair<ll, ll>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ld long double
#define sz(a) ((ll)(a).size())
using namespace std;

const ll maxn=100005;
ll a[maxn], b[maxn], c[maxn], d[maxn];
map <ll, vector <pair<ll, pll>>> Mp;
map <ll, ll> bit;

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    ll w, h, n, e=0, v=0; cin >> w >> h >> n;
    for (ll i=1; i<=n+4; i++)
    {
        if (i<=n) cin >> a[i] >> b[i] >> c[i] >> d[i];
        if (i==n+1) a[i]=0, b[i]=0, c[i]=w, d[i]=0;
        if (i==n+2) a[i]=0, b[i]=0, c[i]=0, d[i]=h;
        if (i==n+3) a[i]=0, b[i]=h, c[i]=w, d[i]=h;
        if (i==n+4) a[i]=w, b[i]=0, c[i]=w, d[i]=h;
        if (a[i]==c[i])
        {
            e+=d[i]-b[i], v+=d[i]-b[i]+1;
            Mp[b[i]-1].pb({1, {1, a[i]}});
            Mp[d[i]].pb({1, {-1, a[i]}});
            if (i<=n) assert(a[i]>0 && a[i]<w);
        }
        else
        {
            e+=c[i]-a[i], v+=c[i]-a[i]+1;
            Mp[b[i]].pb({2, {a[i], c[i]}});
            if (i<=n) assert(b[i]>0 && b[i]<h);
        }
    }
    auto update=[&](ll l, ll r)
    {
        l++, r++;
        for (; l<=w+1; l+=l&(-l)) bit[l]++;
        for (++r; r<=w+1; r+=r&(-r)) bit[r]--;
    };
    auto query=[&](ll i)
    {
        ll ans=0;
        for (++i; i; i-=i&(-i)) ans+=bit[i];
        return ans;
    };
    for (pair<ll, vector <pair<ll, pll>>> i:Mp)
    {
        vector <pair<ll, pll>> event=i.se;
        sort(event.begin(), event.end(), greater<pair<ll, pll>>());
        for (pair<ll, pll> e:event)
        {
            if (e.fi==2) update(e.se.fi, e.se.se);
            else v+=e.se.fi*query(e.se.se);
        }
    }
    cout << e-v+1 << "\n";
}