#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
#include<array>
#include<chrono>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
//ll mod = 1;
constexpr ll mod = 998244353;
//constexpr ll mod = 1000000007;
const int mod17 = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int>P;

#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;

using ld = long double;
typedef pair<ld, ld> LDP;
const ld eps = 1e-10;
const ld pi = acosl(-1.0);

template<typename T>
void chmin(T& a, T b) {
    a = min(a, b);
}
template<typename T>
void chmax(T& a, T b) {
    a = max(a, b);
}
template<typename T>
vector<T> vmerge(vector<T>& a, vector<T>& b) {
    vector<T> res;
    int ida = 0, idb = 0;
    while (ida < a.size() || idb < b.size()) {
        if (idb == b.size()) {
            res.push_back(a[ida]); ida++;
        }
        else if (ida == a.size()) {
            res.push_back(b[idb]); idb++;
        }
        else {
            if (a[ida] < b[idb]) {
                res.push_back(a[ida]); ida++;
            }
            else {
                res.push_back(b[idb]); idb++;
            }
        }
    }
    return res;
}
template<typename T>
void cinarray(vector<T>& v) {
    rep(i, v.size())cin >> v[i];
}
template<typename T>
void coutarray(vector<T>& v) {
    rep(i, v.size()) {
        if (i > 0)cout << " "; cout << v[i];
    }
    cout << "\n";
}
ll mod_pow(ll x, ll n, ll m = mod) {
    if (n < 0) {
        ll res = mod_pow(x, -n, m);
        return mod_pow(res, m - 2, m);
    }
    if (abs(x) >= m)x %= m;
    if (x < 0)x += m;
    //if (x == 0)return 0;
    ll res = 1;
    while (n) {
        if (n & 1)res = res * x % m;
        x = x * x % m; n >>= 1;
    }
    return res;
}
//mod should be <2^31
struct modint {
    int n;
    modint() :n(0) { ; }
    modint(ll m) {
        if (m < 0 || mod <= m) {
            m %= mod; if (m < 0)m += mod;
        }
        n = m;
    }
    operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
bool operator<(modint a, modint b) { return a.n < b.n; }
modint operator+=(modint& a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= (int)mod; return a; }
modint operator-=(modint& a, modint b) { a.n -= b.n; if (a.n < 0)a.n += (int)mod; return a; }
modint operator*=(modint& a, modint b) { a.n = ((ll)a.n * b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, ll n) {
    if (n == 0)return modint(1);
    modint res = (a * a) ^ (n / 2);
    if (n % 2)res = res * a;
    return res;
}

ll inv(ll a, ll p) {
    return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }
modint operator/=(modint& a, modint b) { a = a / b; return a; }
const int max_n = 1 << 20;
modint fact[max_n], factinv[max_n];
void init_f() {
    fact[0] = modint(1);
    for (int i = 0; i < max_n - 1; i++) {
        fact[i + 1] = fact[i] * modint(i + 1);
    }
    factinv[max_n - 1] = modint(1) / fact[max_n - 1];
    for (int i = max_n - 2; i >= 0; i--) {
        factinv[i] = factinv[i + 1] * modint(i + 1);
    }
}
modint comb(int a, int b) {
    if (a < 0 || b < 0 || a < b)return 0;
    return fact[a] * factinv[b] * factinv[a - b];
}
modint combP(int a, int b) {
    if (a < 0 || b < 0 || a < b)return 0;
    return fact[a] * factinv[a - b];
}

ll gcd(ll a, ll b) {
    a = abs(a); b = abs(b);
    if (a < b)swap(a, b);
    while (b) {
        ll r = a % b; a = b; b = r;
    }
    return a;
}
template<typename T>
void addv(vector<T>& v, int loc, T val) {
    if (loc >= v.size())v.resize(loc + 1, 0);
    v[loc] += val;
}
/*const int mn = 2000005;
bool isp[mn];
vector<int> ps;
void init() {
    fill(isp + 2, isp + mn, true);
    for (int i = 2; i < mn; i++) {
        if (!isp[i])continue;
        ps.push_back(i);
        for (int j = 2 * i; j < mn; j += i) {
            isp[j] = false;
        }
    }
}*/

//[,val)
template<typename T>
auto prev_itr(set<T>& st, T val) {
    auto res = st.lower_bound(val);
    if (res == st.begin())return st.end();
    res--; return res;
}

//[val,)
template<typename T>
auto next_itr(set<T>& st, T val) {
    auto res = st.lower_bound(val);
    return res;
}
using mP = pair<modint, modint>;
mP operator+(mP a, mP b) {
    return { a.first + b.first,a.second + b.second };
}
mP operator+=(mP& a, mP b) {
    a = a + b; return a;
}
mP operator-(mP a, mP b) {
    return { a.first - b.first,a.second - b.second };
}
mP operator-=(mP& a, mP b) {
    a = a - b; return a;
}
LP operator+(LP a, LP b) {
    return { a.first + b.first,a.second + b.second };
}
LP operator+=(LP& a, LP b) {
    a = a + b; return a;
}
LP operator-(LP a, LP b) {
    return { a.first - b.first,a.second - b.second };
}
LP operator-=(LP& a, LP b) {
    a = a - b; return a;
}

mt19937 mt(time(0));

const string drul = "DRUL";
string senw = "SENW";
//DRUL,or SENW
//int dx[4] = { 1,0,-1,0 };
//int dy[4] = { 0,1,0,-1 };

//-----------------------------------------


//0:-,1:|,2:/,3:
struct Data {
    int lx, rx, ly, ry;
    int dif, sum;
};
void deb(Data d) {
    cout << d.lx << " " << d.rx << " " << d.ly << " " << d.ry << " " << d.dif << " " << d.sum << "\n";
}
const int z = -mod17;
Data merge(Data a, Data b) {
    Data res;
    res.lx = max(a.lx, b.lx);
    res.rx = min(a.rx, b.rx);
    res.ly = max(a.ly, b.ly);
    res.ry = min(a.ry, b.ry);
    res.dif = z;
    res.sum = z;
    if (a.dif != z)res.dif = a.dif;
    if (b.dif != z)res.dif = b.dif;
    if (a.dif != z && b.dif != z && a.dif != b.dif) {
        res.lx = mod17;
    }
    if (a.sum != z)res.sum = a.sum;
    if (b.sum != z)res.sum = b.sum;
    if (a.sum != z && b.sum != z && a.sum != b.sum) {
        res.lx = mod17;
    }
    return res;
}
ll area(Data d) {
    ll dx = d.rx - d.lx + 1;
    ll dy = d.ry - d.ly + 1;
    if (dx <= 0 || dy <= 0)return 0;
    if (d.dif != z && d.sum != z) {
        int ny = ((ll)d.dif + d.sum) / 2;
        int nx = d.sum - ny;
        if (d.lx <= nx && nx <= d.rx && d.ly <= ny && ny <= d.ry) {
            return 1;
        }
        else {
            return 0;
        }
    }
    else if (d.dif != z) {
        int le = max(d.lx, d.ly - d.dif);
        int ri = min(d.rx, d.ry - d.dif);
        if (le > ri)return 0;
        return ri - le + 1;
    }
    else if (d.sum != z) {
        int le = max(d.lx,d.sum - d.ry);
        int ri = min(d.rx, d.sum - d.ly);
        if (le > ri)return 0;
        return ri - le + 1;
    }
    else {
        return dx * dy;
    }
}


int w, h;
Data rev(Data d) {
    Data res;
    res.lx = d.lx;
    res.rx = d.rx;
    res.ly = h + 1 - d.ry;
    res.ry = h + 1 - d.ly;
    if (d.sum == z) {
        res.dif = z;
    }
    else {
        res.dif = h + 1 - d.sum;
    }
    if (d.dif == z) {
        res.sum = z;
    }
    else {
        res.sum = h + 1 - res.dif;
    }
    return res;
}
vector<Data> ss(P a, P b) {
    vector<Data> res;
    if (a > b)swap(a, b);
    if (a.first == b.first) {
        Data d;
        d.lx = 1;
        d.rx = w;
        d.ly = (a.second + b.second) / 2;
        d.ry = d.ly;
        d.dif = z;
        d.sum = z;
        res.push_back(d);
    }
    else if (a.second == b.second) {
        Data d;
        d.lx = (a.first + b.first) / 2;
        d.rx = d.lx;
        d.ly = 1;
        d.ry = h;
        d.dif = z;
        d.sum = z;
        res.push_back(d);
    }
    else {
        if (a.second < b.second) {
            if (b.first - a.first < b.second - a.second) {
                int sum = b.first - a.first + b.second - a.second;
                Data d;
                d.lx = 1;
                d.rx = a.first - 1;
                d.ly = a.first + sum / 2;
                d.ry = d.ly;
                d.dif = z;
                d.sum = z;
                res.push_back(d);
                d.lx = b.first + 1;
                d.rx = w;
                d.ly = b.second - sum / 2;
                d.ry = d.ly;
                d.dif = z;
                d.sum = z;
                res.push_back(d);
                d.lx = a.first;
                d.rx = b.first;
                d.ly = b.second - sum / 2;
                d.ry = a.second + sum / 2;
                d.dif = z;
                d.sum = a.first + a.second + sum / 2;
                res.push_back(d);
            }
            else if (b.first - a.first == b.second - a.second) {
                Data d;
                d.lx = 1;
                d.rx = a.first;
                d.ly = b.second;
                d.ry = h;
                d.dif = z;
                d.sum = z;
                res.push_back(d);
                d.lx = b.first;
                d.rx = w;
                d.ly = 1;
                d.ry = a.second;
                d.dif = z;
                d.sum = z;
                res.push_back(d);
                d.lx = a.first + 1;
                d.rx = b.first - 1;
                d.ly = a.second + 1;
                d.ry = b.second - 1;
                d.sum = a.first + b.second;
                d.dif = z;
                res.push_back(d);
            }
            else {
                int sum = b.first - a.first + b.second - a.second;
                Data d;
                d.lx = b.first - sum / 2;
                d.rx = d.lx;
                d.ly = b.second + 1;
                d.ry = h;
                d.sum = z;
                d.dif = z;
                res.push_back(d);
                d.lx = a.first + sum / 2;
                d.rx = d.lx;
                d.ly = 1;
                d.ry = a.second - 1;
                d.sum = z;
                d.dif = z;
                res.push_back(d);
                d.lx = b.first - sum / 2;
                d.rx = a.first + sum / 2;
                d.ly = a.second;
                d.ry = b.second;
                d.sum = a.first + sum / 2 + a.second;
                d.dif = z;
                res.push_back(d);
            }
        }
        else {
            a.second = h + 1 - a.second;
            b.second = h + 1 - b.second;

            auto vd = ss(a, b);
            rep(i, vd.size()) {
                vd[i] = rev(vd[i]);
            }

            res = vd;
        }
    }
    return res;
}
void solve() {
    cin >> w >> h;
    int n; cin >> n;
    vector<int> x(n), y(n);
    rep(i, n)cin >> x[i] >> y[i];
    vector<Data> vd;
    Data ori;
    ori.lx = 1;
    ori.rx = w;
    ori.ly = 1;
    ori.ry = h;
    ori.dif = z;
    ori.sum = z;
    vd.push_back(ori);
    rep(i, n - 1) {
        int c = 0;
        if (x[i] % 2)c ^= 1;
        if (y[i] % 2)c ^= 1;
        if (x[i+1] % 2)c ^= 1;
        if (y[i + 1] % 2)c ^= 1;
        if (c) {
            cout << 0 << "\n"; return;
        }
        auto ds = ss({ x[i],y[i] }, { x[i + 1],y[i + 1] });
        vector<Data> nvd;
        rep(i, vd.size())rep(j, ds.size()) {
            Data ad = merge(vd[i], ds[j]);
            if (area(ad) > 0) {
                nvd.push_back(ad);
            }
        }
        swap(vd, nvd);
        /*cout << "hello\n";
        rep(i, vd.size()) {
            deb(vd[i]);
        }
        cout << vd.size() << "\n";*/
    }
    ll ans = 0;
    rep(i, vd.size()) {
        ans += area(vd[i]);
    }
    cout << ans << "\n";
}





signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(10);
    //init_f();
    //init();
    //while(true)
    //expr();
    //int t; cin >> t; rep(i, t)
    solve();
    return 0;
}