#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Pii = pair<int, int>;
using Vi = vector<int>;
void run();
int main() {
  cin.sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(18);
  run();
  return 0;
}
int uplg(int n) { return 32 - __builtin_clz(n); }
int uplg(ll n) { return 64 - __builtin_clzll(n); }
struct Banned {
  int begin, end, height, cost;
  bool operator<(const Banned& r) const { return height < r.height; }
};
int dp[51][51][51];
vector<Banned> bans;
int solve(int begin, int end, int height) {
  int& ret = dp[begin][end][height];
  if (ret >= 0) return ret;
  ret = 0;
  for (int i = (begin); i < (end); i++) {
    int cost = 0, j = 0;
    for (int h = (0); h < (height + 1); h++) {
      while (j < int((bans).size())) {
        auto& b = bans[j];
        if (b.height >= h) break;
        if (b.begin >= begin && b.end <= end && b.begin <= i &&
            b.end >= i + 1) {
          cost += b.cost;
        }
        j++;
      }
      ret = max(ret, solve(begin, i, h) + solve(i + 1, end, h) - cost + h * h);
    }
  }
  return ret;
}
void run() {
  int n, h, m;
  cin >> n >> h >> m;
  bans.resize(m);
  for (auto& b : (bans)) {
    cin >> b.begin >> b.end >> b.height >> b.cost;
    b.begin--;
  }
  sort((bans).begin(), (bans).end());
  for (int i = (0); i < (n + 1); i++)
    for (int j = (0); j < (n + 1); j++)
      for (int k = (0); k < (h + 1); k++) dp[i][j][k] = -1;
  cout << solve(0, n, h) << endl;
}
