#include<bits/stdc++.h>
#define pb push_back
using namespace std;
const int MAXN = 34004;
struct Edge {int to, flow;};
int s, t, P[MAXN], D[MAXN], qu[MAXN];
vector < int > Adj[MAXN];
vector < Edge > E;
int ptr, mm;
inline void AddEdge(int v, int u, int w)
{
Adj[v].pb(E.size());
E.pb({u, w});
Adj[u].pb(E.size());
E.pb({v, 0});
}
inline bool BFS()
{
int l = 0, r = 0;
memset(D, -1, sizeof(D));
memset(P, 0, sizeof(P));
qu[r ++] = s; D[s] = 0;
while (r - l)
{
int v = qu[l ++];
for (int i = 0; i < (int)Adj[v].size(); i++)
{
int id = Adj[v][i];
if (mm < E[id].to && E[id].to <= ptr)
swap(Adj[v][i], Adj[v].back()), Adj[v].pop_back(), i --;
else if (E[id].flow && D[E[id].to] == -1)
{
D[E[id].to] = D[v] + 1;
if (E[id].to == t)
return (1);
qu[r ++] = E[id].to;
}
}
}
return (0);
}
int DFS(int v, int flow)
{
if (v == t)
return (flow);
int Flow = 0;
for (int i = P[v]; i < (int)Adj[v].size(); i++)
{
int id = Adj[v][i];
if (E[id].flow && D[E[id].to] == D[v] + 1)
{
int _flow = DFS(E[id].to, min(flow, E[id].flow));
if (!_flow)
swap(Adj[v][i], Adj[v][P[v]]), P[v] ++;
E[id].flow -= _flow;
E[id^1].flow += _flow;
Flow += _flow; flow -= _flow;
if (!flow) return (Flow);
}
else
swap(Adj[v][i], Adj[v][P[v]]), P[v] ++;
}
return (Flow);
}
inline int MaxFlow()
{
int Flow = 0;
while (BFS())
Flow += DFS(s, INT_MAX);
return Flow;
}
int n, m, k;
vector < int > vec[MAXN];
inline void Add(int v)
{
AddEdge(v + m, t, 1);
for (int &u : vec[v])
AddEdge(u, v + m, 1);
}
inline int Del(int v)
{
v += m;
for (int &id : Adj[v])
if (E[id].to == t)
{
if (E[id^1].flow == 1)
{
int e = -1;
for (int &idd : Adj[v])
if (E[idd].flow)
{e = idd; break;}
assert(e != -1);
int u = E[e].to;
E[e].flow -= 1;
E[e^1].flow += 1;
E[id^1].flow = 0;
for (int &idd : Adj[u])
if (E[idd].to == s)
{
E[idd].flow = 0;
E[idd^1].flow = 1;
return (1);
}
assert(0);
}
else
{E[id].flow = 0; return (0);}
}
assert(0);
}
int main()
{
scanf("%d%d%d", &n, &m, &k);
int source = 0, sink = n + m + 1;
s = source; t = sink;
for (int i = 1; i <= m; i++)
AddEdge(source, i, 1);
for (int i = 1; i <= k; i++)
{
int v, u;
scanf("%d%d", &v, &u);
vec[v].pb(u);
//AddEdge(u, v + m, 1);
}
srand(time(0));
for (int i = 1; i <= n; i++)
random_shuffle(vec[i].begin(), vec[i].end());
int r = 0, Flow = 0;
int tot = 0;
ptr = mm = m;
for (int l = 1; l <= n; l ++)
{
while (r < l)
r ++, Add(r);
Flow += MaxFlow();
while (r < n && Flow < m)
r ++, Add(r), Flow += MaxFlow();
if (Flow < m)
break;
tot += n - r + 1;
Flow -= Del(l);
ptr ++;
}
return !printf("%d\n", tot);
}
