#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define FOR(var, begin, end) for (int var = (begin); var <= (end); var++)
#define RFOR(var, begin, end) for (int var = (begin); var >= (end); var--)
#define REP(var, length) FOR(var, 0, length - 1)
#define RREP(var, length) RFOR(var, length - 1, 0)
#define EACH(value, var) for (auto value : var)
#define SORT(var) sort(var.begin(), var.end())
#define REVERSE(var) reverse(var.begin(), var.end())
#define RSORT(var) \
  SORT(var);       \
  REVERSE(var)
#define OPTIMIZE_STDIO         \
  ios::sync_with_stdio(false); \
  cin.tie(0);                  \
  cout.precision(10);          \
  cout << fixed
#define endl '\n'

const int INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;
struct mint {
  ll x;
  mint() : x(0) {
  }
  mint(ll x) : x((x % MOD + MOD) % MOD) {
  }
  mint& operator+=(const mint& r) {
    if ((x += r.x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  mint& operator-=(const mint& r) {
    if ((x -= r.x) < 0) {
      x += MOD;
    }
    return *this;
  }
  mint& operator*=(const mint& r) {
    if ((x *= r.x) > MOD) {
      x %= MOD;
    }
    return *this;
  }
  mint& operator++() {
    if ((++x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  mint operator++(int) {
    mint ret = x;
    if ((++x) >= MOD) {
      x -= MOD;
    }
    return ret;
  }
  mint& operator--() {
    if ((--x) < 0) {
      x += MOD;
    }
    return *this;
  }
  mint operator--(int) {
    mint ret = x;
    if ((--x) < 0) {
      x += MOD;
    }
    return ret;
  }
  mint operator+(const mint& r) {
    mint ret;
    return ret = x + r.x;
  }
  mint operator-(const mint& r) {
    mint ret;
    return ret = x - r.x;
  }
  mint operator*(const mint& r) {
    mint ret;
    return ret = x * r.x;
  }
  mint operator-() {
    return mint() - *this;
  }
  bool operator<(const mint& a) {
    return x < a.x;
  }
  bool operator>(const mint& a) {
    return x > a.x;
  }
  bool operator<=(const mint& a) {
    return x <= a.x;
  }
  bool operator>=(const mint& a) {
    return x >= a.x;
  }
  bool operator==(const mint& a) {
    return x == a.x;
  }
  bool operator!=(const mint& a) {
    return x != a.x;
  }
};
ostream& operator<<(ostream& os, const mint& r) {
  os << r.x;
  return os;
}
ostream& operator>>(ostream& os, const mint& r) {
  os >> r.x;
  return os;
}

int q;
vector<int> a;
vector<int> b;
vector<int> c;
vector<int> d;
vector<int> buf;
int ans;

void dfs(int i, const int size, const int range_start, const int range_end)
{
  if (i == size) {
    int sum = 0;
    // Aの候補配列が完成
    REP(i, q) {
      if (- buf[a[i] - 1] + buf[b[i] - 1] != c[i]) continue;
      sum += d[i];
    }
    ans = max(ans, sum);

    //REP (i, buf.size()) {
    //  cout << buf[i] << " ";
    //}
    //cout << endl;
  } else {
    FOR(j, range_start, range_end) {
      buf[i] = j;
      dfs(i + 1, size, j, range_end);
    }
  }
}


void solve(istream& cin, ostream& cout) {
  int n, m;
  cin >> n >> m >> q;
  a.resize(q);
  b.resize(q);
  c.resize(q);
  d.resize(q);
  REP(i, q) {
    cin >> a[i] >> b[i] >> c[i] >> d[i];
  }
  buf.resize(n);
  ans = -1;
  dfs(0, n, 1, m);
  cout << ans << endl;
}

#ifndef TEST
int main() {
  OPTIMIZE_STDIO;
  solve(cin, cout);
  return 0;
}
#endif


Measured memory_bytes: 3664