#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void rd(T &x) {
  char ch;
  x = 0;
  bool fl = false;
  while (!isdigit(ch = getchar())) (ch == '-') && (fl = true);
  for (x = (ch ^ '0'); isdigit(ch = getchar()); x = x * 10 + (ch ^ '0'))
    ;
  (fl == true) && (x = -x);
}
template <class T>
inline void output(T x) {
  if (x / 10) output(x / 10);
  putchar(x % 10 + '0');
}
template <class T>
inline void ot(T x) {
  if (x < 0) putchar('-'), x = -x;
  output(x);
  putchar(' ');
}
template <class T>
inline void prt(T a[], int st, int nd) {
  for (register int i = st; i <= nd; ++i) ot(a[i]);
  putchar('\n');
}
namespace Miracle {
const int N = 55;
const int P = N * N;
const int inf = 0x3f3f3f3f;
int n, m, h;
int s, t;
struct node {
  int nxt, to;
  int w;
} e[2 * (P + P + N * N)];
int hd[P], cnt = 1;
void add(int x, int y, int z) {
  e[++cnt].nxt = hd[x];
  e[cnt].to = y;
  e[cnt].w = z;
  hd[x] = cnt;
  e[++cnt].nxt = hd[y];
  e[cnt].to = x;
  e[cnt].w = 0;
  hd[y] = cnt;
}
int d[P];
int q[P], l, r;
int ans;
int dfs(int x, int flow) {
  int res = flow;
  if (x == t) return flow;
  for (register int i = hd[x]; i && res; i = e[i].nxt) {
    int y = e[i].to;
    if (d[y] == d[x] + 1 && e[i].w) {
      int k = dfs(y, min(res, e[i].w));
      if (!k) d[y] = 0;
      res -= k;
      e[i].w -= k;
      e[i ^ 1].w += k;
    }
  }
  return flow - res;
}
bool bfs() {
  memset(d, 0, sizeof d);
  l = 1, r = 0;
  q[++r] = s;
  d[s] = 1;
  while (l <= r) {
    int x = q[l++];
    for (register int i = hd[x]; i; i = e[i].nxt) {
      int y = e[i].to;
      if (e[i].w && !d[y]) {
        d[y] = d[x] + 1;
        q[++r] = y;
        if (y == t) return true;
      }
    }
  }
  return false;
}
int num(int x, int y) { return (x - 1) * (h + 1) + y + 1; }
int main() {
  rd(n);
  rd(h);
  rd(m);
  ans = n * h * h;
  s = 0;
  t = num(n, h) + 1;
  int tot = t;
  for (register int i = 1; i <= n; ++i) {
    add(s, num(i, 0), inf);
    for (register int j = 0; j < h; ++j) {
      add(num(i, j), num(i, j + 1), h * h - j * j);
    }
  }
  int l, r, x, c;
  for (register int i = 1; i <= m; ++i) {
    rd(l);
    rd(r);
    rd(x);
    rd(c);
    if (x < h) {
      ++tot;
      add(tot, t, c);
      for (register int j = l; j <= r; ++j) {
        add(num(j, x + 1), tot, inf);
      }
    }
  }
  int flow = 0;
  while (bfs()) {
    while (flow = dfs(s, inf)) ans -= flow;
  }
  ot(ans);
  return 0;
}
}  // namespace Miracle
signed main() {
  Miracle::main();
  return 0;
}
