#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e9;
const int N = 1000010;
int n, m, h, s, t;
long long ans, res, point, dis[N];
int cnt = 1, cur[N], head[N];
struct edge {
  int to, nxt;
  long long dis;
} e[N << 1];
inline void add(int u, int v, long long w) {
  e[++cnt].to = v;
  e[cnt].dis = w;
  e[cnt].nxt = head[u];
  head[u] = cnt;
  e[++cnt].to = u;
  e[cnt].dis = 0;
  e[cnt].nxt = head[v];
  head[v] = cnt;
}
inline int bfs() {
  memset(dis, 0, sizeof(dis));
  queue<int> q;
  q.push(s);
  dis[s] = 1;
  cur[s] = head[s];
  while (!q.empty()) {
    int x = q.front();
    q.pop();
    for (register int i = head[x]; i; i = e[i].nxt) {
      int v = e[i].to;
      if (e[i].dis > 0 && !dis[v]) {
        q.push(v);
        cur[v] = head[v];
        dis[v] = dis[x] + 1;
        if (v == t) return 1;
      }
    }
  }
  return 0;
}
inline int dfs(int x, long long flow) {
  if (x == t) return flow;
  long long k, rest = flow;
  for (register int i = cur[x]; i && flow; i = e[i].nxt) {
    cur[x] = i;
    int v = e[i].to;
    if (e[i].dis && (dis[v] == dis[x] + 1)) {
      k = dfs(v, min(rest, e[i].dis));
      e[i].dis -= k;
      e[i ^ 1].dis += k;
      rest -= k;
      if (rest == 0) break;
    }
  }
  return flow - rest;
}
inline int idx(int x, int y) { return (x - 1) * (h + 2) + y; }
int main() {
  scanf("%d%d%d", &n, &h, &m);
  t = N - 10;
  for (int i = 1; i <= n; i++) ans += h * h;
  for (register int i = 1; i <= n; i++)
    for (register int j = 1; j <= h + 1; j++)
      add(idx(i, j), idx(i, j + 1), h * h - (j - 1) * (j - 1));
  point = n * (h + 2);
  for (register int i = 1; i <= n; i++) {
    add(s, idx(i, 1), INF);
    add(idx(i, h + 2), t, INF);
  }
  for (int i = 1, l, r, x, c; i <= m; i++) {
    scanf("%d%d%d%d", &l, &r, &x, &c);
    if (x == h) continue;
    ++point;
    add(point, t, c);
    for (register int j = l; j <= r; j++) add(idx(j, x + 2), point, INF);
  }
  while (bfs()) {
    res += dfs(s, INF);
  }
  printf("%lld", ans - res);
  return 0;
}
