#include <bits/stdc++.h>
using namespace std;
const int Maxn = 52;
const int Inf = 1000000000;
int n, h, m;
int L[Maxn], R[Maxn], X[Maxn], C[Maxn];
int seq[Maxn];
int gdp[Maxn][Maxn], dp[Maxn][Maxn];
int res;
bool Less(const int &a, const int &b) { return X[a] < X[b]; }
void Add(int h) {
  for (int l = 0; l < n; l++) {
    for (int r = l; r < n; r++) dp[l][r] = gdp[l][r];
    dp[l][l] = max(dp[l][l], h * h);
    for (int r = l; r < n; r++) {
      if (r + 1 < n) dp[l][r + 1] = max(dp[l][r + 1], dp[l][r] + h * h);
      for (int r2 = r + 1; r2 < n; r2++)
        dp[l][r2] = max(dp[l][r2], dp[l][r] + gdp[r + 1][r2]);
    }
  }
}
int main() {
  scanf("%d %d %d", &n, &h, &m);
  for (int i = 0; i < m; i++) {
    scanf("%d %d %d %d", &L[i], &R[i], &X[i], &C[i]);
    L[i]--;
    R[i]--;
    seq[i] = i;
    res -= C[i];
  }
  sort(seq, seq + m, Less);
  fill((int *)gdp, (int *)gdp + Maxn * Maxn, -Inf);
  for (int i = 0; i < m; i++) {
    int ind = seq[i];
    Add(X[ind]);
    for (int l = 0; l <= L[ind]; l++)
      for (int r = R[ind]; r < n; r++)
        gdp[l][r] = max(gdp[l][r], dp[l][r] + C[ind]);
  }
  Add(h);
  printf("%d\n", res + dp[0][n - 1]);
  return 0;
}
