#include <bits/stdc++.h>
using namespace std;
template <typename TH>
void _dbg(const char* sdbg, TH h) {
  cerr << sdbg << "=" << h << "\n";
}
template <typename TH, typename... TA>
void _dbg(const char* sdbg, TH h, TA... t) {
  while (*sdbg != ',') {
    cerr << *sdbg++;
  }
  cerr << "=" << h << ",";
  _dbg(sdbg + 1, t...);
}
template <class C>
void mini(C& a4, C b4) {
  a4 = min(a4, b4);
}
template <class C>
void maxi(C& a4, C b4) {
  a4 = max(a4, b4);
}
template <class T1, class T2>
ostream& operator<<(ostream& out, pair<T1, T2> pair) {
  return out << "(" << pair.first << ", " << pair.second << ")";
}
template <class A, class B, class C>
struct Triple {
  A first;
  B second;
  C third;
  bool operator<(const Triple& t) const {
    if (first != t.first) return first < t.first;
    if (second != t.second) return second < t.second;
    return third < t.third;
  }
};
template <class T>
void ResizeVec(T&, vector<long long>) {}
template <class T>
void ResizeVec(vector<T>& vec, vector<long long> sz) {
  vec.resize(sz[0]);
  sz.erase(sz.begin());
  if (sz.empty()) {
    return;
  }
  for (T& v : vec) {
    ResizeVec(v, sz);
  }
}
template <class A, class B, class C>
ostream& operator<<(ostream& out, Triple<A, B, C> t) {
  return out << "(" << t.first << ", " << t.second << ", " << t.third << ")";
}
template <class T>
ostream& operator<<(ostream& out, vector<T> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
template <class T>
ostream& operator<<(ostream& out, set<T> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
template <class L, class R>
ostream& operator<<(ostream& out, map<L, R> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
const long long N = 55;
long long dp[N][N][N];
long long lb[N], rb[N], x[N], c[N];
long long intvs;
long long Rec(long long l, long long r, long long h) {
  if (h == 0) {
    return 0;
  }
  if (l > r) {
    return 0;
  }
  if (dp[l][r][h] != -1) {
    return dp[l][r][h];
  }
  long long cand = Rec(l, r, h - 1);
  for (long long m = (l); m <= (r); ++m) {
    long long fine = 0;
    for (long long i = (1); i <= (intvs); ++i) {
      if (l <= lb[i] && lb[i] <= m && m <= rb[i] && rb[i] <= r && h > x[i]) {
        fine += c[i];
      }
    }
    maxi(cand, h * h + Rec(l, m - 1, h) + Rec(m + 1, r, h) - fine);
  }
  return dp[l][r][h] = cand;
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  if (0) cout << fixed << setprecision(10);
  cin.tie(0);
  for (long long i = 0; i < (N); ++i) {
    for (long long j = 0; j < (N); ++j) {
      for (long long k = 0; k < (N); ++k) {
        dp[i][j][k] = -1;
      }
    }
  }
  long long n, h;
  cin >> n >> h >> intvs;
  for (long long i = (1); i <= (intvs); ++i) {
    cin >> lb[i] >> rb[i] >> x[i] >> c[i];
  }
  cout << Rec(1, n, h) << endl;
  return 0;
}
