#include <bits/stdc++.h>
#define fi first
#define se second
#define all(v) v.begin() , v.end()
#define sz(v) int(v.size())
#define unq(v) sort(all(v)); v.resize(unique(all(v)) - v.begin());
using namespace std;

typedef long long ll;
typedef pair<int , int> ii;
typedef pair<long long , int> lli;

const int maxN = int(2e5)+7;

void solve(){
    int n , m , k;
    cin >> n >> m >> k;
    ll ans = (n + m);
    for (int i = 1 ; i <= k ; i++){
        int x , y , u , v;
        cin >> x >> y >> u >> v;
        ans += 1ll * (abs(x - u) + abs(y - v));
    }
    cout << ans - 2ll * (k + 1) << "\n"; 
}

#define name "F"

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(name".INP" , "r")){
        freopen(name".INP" , "r" , stdin);
        freopen(name".OUT" , "w" , stdout);
    }
    int t = 1; //cin >> t;
    while (t--) solve();
    return 0;
}