#include <stdio.h>
#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <string>
#include <queue>
#include <map>
#include <set>
#include <cmath>
#include <sstream>
#include <stack>
#include <string.h>

#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define PI 3.14159265358979
#define forn(i, n) for(int i = 0; i < n; ++i)
#define ALL(x) x.begin(), x.end()
#define L(s) (int)((s).size())
#define ms(x) memset(x,0,sizeof(x))
#define del(y,x) erase(y.begin()+x)

typedef long long ll;
using namespace std;
typedef pair<int,int> pii;
const int INF = 2147483647;
const ll LLINF = 9223372036854775807LL;
const int ST = 100010;
const int ST1 = 1000010;
const ll MOD = 1000000007;

ll ABS(ll a)
{
    if(a<0)
        return a*(-1);
    else
        return a;
}


vector<int> xs;
vector<int> ys;
vector<pii> kor;
map<ll,ll> dig;
vector<ll> lol;
int main()
{
#ifndef ONLINE_JUDGE
    freopen("darts.in", "r", stdin);
    freopen("darts.out", "w", stdout);
#endif
    int n,m,k;
    cin >> n >> m >> k;
    ll ans = 0;
    int x,y;
    for(int i = 0;i < k;i++)
    {
        cin >> x >> y;
        xs.pb(x);
        ys.pb(y);
    }
    xs.pb(0);
    ys.pb(0);
    xs.pb(n);
    ys.pb(m);
    sort(ALL(xs));
    sort(ALL(ys));
    vector<int>::iterator it = unique(ALL(xs));
    xs.resize(it-xs.begin());
    it = unique(ALL(ys));
    ys.resize(it-ys.begin());

    for(int i = 0;i < L(xs);i++)
    {
        for(int j = 0;j < L(ys);j++)
        {
            ll l = xs[i]-ys[j];
            lol.pb(l);
        }
    }
    sort(ALL(lol));
    lol.pb(LLINF);
    for(int i = 0;i < L(lol)-1;i++)
    {
        ll k = 0;
        while(lol[i]==lol[i+1])
        {
            i++;
            k++;
        }
        ans+=(1+k)*k/2;
    }
    cout << ans;
}