#include <bits/stdc++.h>
using namespace std;
inline void read(int &x) {
  int v = 0, f = 1;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
inline void read(long long &x) {
  long long v = 0ll, f = 1ll;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
inline void readc(char &x) {
  char c;
  while ((c = getchar()) == ' ')
    ;
  x = c;
}
inline void writes(string s) { puts(s.c_str()); }
inline void writeln() { writes(""); }
inline void writei(int x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
inline void writell(long long x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
int n, h, m, i, j, dis[3005], cnt, ans, s = 0, t = 3001;
vector<int> e[3005];
struct edg {
  int y, z;
} a[1111111];
void add(int x, int y, int z) {
  cnt++;
  e[x].push_back(cnt * 2 - 2);
  e[y].push_back(cnt * 2 - 1);
  a[cnt * 2 - 2] = (edg){y, z};
  a[cnt * 2 - 1] = (edg){x, 0};
}
int id(int x, int y) { return (x - 1) * h + y; }
bool bfs(int s, int t) {
  queue<int> q;
  memset((dis), (0x16), (sizeof((dis))));
  dis[s] = 0;
  q.push(s);
  while (!q.empty()) {
    int x = q.front();
    q.pop();
    for (__typeof((e[x]).begin()) it = (e[x]).begin(); it != (e[x]).end(); it++)
      if (a[*it].z) {
        if (dis[a[*it].y] > dis[x] + 1) {
          dis[a[*it].y] = dis[x] + 1;
          q.push(a[*it].y);
        }
      }
  }
  return dis[t] < dis[t + 1];
}
int dfs(int x, int tt, int flw) {
  if (x == tt || !flw) return flw;
  int ans = 0;
  for (__typeof((e[x]).begin()) it = (e[x]).begin(); it != (e[x]).end(); it++) {
    if (a[*it].z && dis[x] + 1 == dis[a[*it].y]) {
      int t = dfs(a[*it].y, tt, min(flw, a[*it].z));
      ans += t;
      flw -= t;
      a[*it].z -= t;
      a[(*it) ^ 1].z += t;
    }
    if (!flw) break;
  }
  if (flw) dis[x] = -1;
  return ans;
}
int dinic(int s, int t) {
  int ans = 0;
  while (bfs(s, t)) {
    ans += dfs(s, t, 0x3bbbbbbb);
  }
  return ans;
}
int main() {
  read(n);
  read(h);
  read(m);
  for (((i)) = (1); ((i)) <= ((n)); ((i))++) {
    for (((j)) = (1); ((j)) <= ((h)); ((j))++) {
      if (j < h) add(id(i, j + 1), id(i, j), 0x3bbbbbbb);
      add(s, id(i, j), j * 2 - 1);
      ans += j * 2 - 1;
    }
  }
  for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
    int l, r, ys, c;
    read(l);
    read(r);
    read(ys);
    read(c);
    if (ys < h)
      for ((j) = (l); (j) <= (r); (j)++) {
        add(id(j, ys + 1), i + 2500, 0x3bbbbbbb);
      }
    add(i + 2500, t, c);
  }
  cout << ans - dinic(s, t) << endl;
  return 0;
}
