# include <bits/stdc++.h>
# define pb push_back
# define fr first
# define sc second
# define mk make_pair
using namespace std;
const int inf = 1e9 + 7;
const int N = 1e6 + 5;
typedef long long ll;
int n, m, k, used[N], mt[N], lo, ri;
ll ans;
vector <int> g[N];
bool try_kuhn(int v)
{
if(used[v]) return false;
used[v] = 1;
for(int to : g[v])
{
if((mt[to] == -1 || try_kuhn(mt[to])) && to >= lo && to <= ri)
{
mt[to] = v;
return true;
}
}
return false;
}
bool check(int l, int r)
{
for(int i = 1; i < l; i ++)
used[i] = 1;
for(int i = r + 1; i <= n; i ++)
used[i] = 1;
for(int i = 1; i <= n + m; i ++)
mt[i] = -1;
lo = l, ri = r;
for(int i = 1; i <= m; i ++)
{
for(int j = l; j <= r; j ++)
used[j] = 0;
for(int j = 1; j <= m; j ++)
used[j + n] = 0;
try_kuhn(i + n);
}
for(int i = l; i <= r; i ++)
{
if(mt[i] == -1) continue;
mt[mt[i]] = 1;
}
for(int i = 1; i <= m; i ++)
if(mt[i + n] == -1) return false;
return true;
}
int main()
{
cin >> n >> m >> k;
for(int i = 1; i <= k; i ++)
{
int a, b;
cin >> a >> b;
g[a].pb(n + b);
g[n + b].pb(a);
}
for(int i = 1; i <= n; i ++)
{
int l = i, r = n;
while(r - l > 1)
{
int md = (l + r) >> 1;
if(check(i, md))
r = md;
else
l = md;
}
if(check(i, l))
r = l;
if(check(i, r))
ans += (n - r + 1);
}
cout << ans << endl;
}
