#include <bits/stdc++.h>

#define int long long

using namespace std;

const int maxn = 200005;
int tree[maxn], hm[maxn], wm[maxn];
vector<int> vec[maxn];
void add(int k, int v) {
    k++;
    for (int i = k; i < maxn; i+=i&-i) tree[i] += v;
}
int qry(int k) {
    k++;
    int res = 0;
    for (int i = k; i >= 1; i-=i&-i) res += tree[i];
    return res;
}

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    for (int i = 0; i < maxn; i++) tree[i] = 0;
    int h, w, m;
    cin >> h >> w >> m;
    for (int i = 0; i <= h; i++) hm[i] = w;
    for (int i = 0; i <= w; i++) wm[i] = h;
    for (int i = 0; i < m; i++) {
        int x, y;
        cin >> x >> y;
        hm[x] = min(hm[x], y-1);
        wm[y] = min(wm[y], x-1);
    }
    for (int i = 1; i <= h; i++) if (hm[i-1] == 0) hm[i] = 0;
    for (int i = 1; i <= w; i++) if (wm[i-1] == 0) wm[i] = 0;
    int res = 0;
    for (int i = 1; i <= h; i++) {
        res += hm[i];
        if (hm[i] != 0) vec[hm[i]].push_back(i);
        else add(i,1);
    }
    for (int i = 1; i <= w; i++) {
        if (wm[i] != 0) res += qry(wm[i]);
        for (int p : vec[i]) add(p, 1);
    }
    cout << res << '\n';
}
/*

 */
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n)  for(long long i=0;i<(long long)(n);i++)
#define REP(i,k,n) for(long long i=k;i<(long long)(n);i++)
#define all(a) a.begin(),a.end()
#define rsort(a) {sort(all(a));reverse(all(a));}
#define pb emplace_back
#define eb emplace_back
#define lb(v,k) (lower_bound(all(v),k)-v.begin())
#define ub(v,k) (upper_bound(all(v),k)-v.begin())
#define fi first
#define se second
#define pi M_PI
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T,vector<T>,greater<T>>
#define dame(a) {out(a);return 0;}
#define decimal cout<<fixed<<setprecision(15);
#define dupli(a) {sort(all(a));a.erase(unique(all(a)),a.end());}
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> PP;
typedef tuple<ll,ll,ll,ll> PPP;
typedef multiset<ll> S;
using vi=vector<ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vvvvi=vector<vvvi>;
using vp=vector<P>;
using vvp=vector<vp>;
using vb=vector<bool>;
using vvb=vector<vb>;
const ll inf=1001001001001001001;
const ll INF=1001001001;
const ll mod=1000000007;
const double eps=1e-10;
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outp(T a){cout<<'('<<a.fi<<','<<a.se<<')'<<'\n';}
template<class T> void outvp(T v){rep(i,v.size())cout<<'('<<v[i].fi<<','<<v[i].se<<')';cout<<'\n';}
template<class T> void outvvp(T v){rep(i,v.size())outvp(v[i]);}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){rep(i,v.size())outv(v[i]);}
template<class T> bool isin(T x,T l,T r){return (l)<=(x)&&(x)<=(r);}
template<class T> void yesno(T b){if(b)out("yes");else out("no");}
template<class T> void YesNo(T b){if(b)out("Yes");else out("No");}
template<class T> void YESNO(T b){if(b)out("YES");else out("NO");}
template<class T> void noyes(T b){if(b)out("no");else out("yes");}
template<class T> void NoYes(T b){if(b)out("No");else out("Yes");}
template<class T> void NOYES(T b){if(b)out("NO");else out("YES");}
void outs(ll a,ll b){if(a>=inf-100)out(b);else out(a);}
ll gcd(ll a,ll b){if(b==0)return a;return gcd(b,a%b);}
ll modpow(ll a,ll b){ll res=1;a%=mod;while(b){if(b&1)res=res*a%mod;a=a*a%mod;b>>=1;}return res;}
vi seg;
ll N;
void init(vi v){
    N=1;
    while(N<v.size())N*=2;
    seg=vi(N*2-1);
    rep(i,v.size())seg[i+N-1]=v[i];
    for(int i=N-2;i>=0;i--)seg[i]=seg[i*2+1]+seg[i*2+2];
}
void update(ll i,ll x){
    i=N+i-1;
    seg[i]=x;
    while(i>0){
        i=(i-1)/2;
        seg[i]=seg[i*2+1]+seg[i*2+2];
    }
}
ll getsum(ll a,ll b,ll k,ll l,ll r){
    if(r<=a||b<=l)return 0;
    if(a<=l&&r<=b)return seg[k];
    ll c1=getsum(a,b,k*2+1,l,(l+r)/2);
    ll c2=getsum(a,b,k*2+2,(l+r)/2,r);
    return c1+c2;
}
int main(){
    ll h,w,n;cin>>h>>w>>n;
    ll c=w,d=h;
    vvi g(w);
    ll ans=0;
    ll mi=h;
    rep(i,n){
        ll a,b;cin>>a>>b;a--;b--;
        g[b].pb(a);
        if(!b)chmin(mi,a);
    }
    vi t(mi,1);
    init(t);
    bool ok=true;
    rep(i,w){
        sort(all(g[i]));
        for(ll x:g[i])if(x<mi)update(x,0);
        if(g[i].size()&&g[i][0]==0)ok=false;
        if(g[i].size()&&ok){
            // out('A');
            ans+=g[i][0]+getsum(g[i][0],N,0,0,N);
        }
        else if(ok){
            ans+=h;
            // out('B');
        }
        else{
            ans+=getsum(0,N,0,0,N);
            // out('C');
        }
    }
    out(ans);
}