Problem p02695 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <climits>
#include <cmath>
#include <cstring>
#include <functional>
#include <iostream>
#include <limits.h>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vector>
using namespace std;

#define intmax INT_MAX
#define lmax LONG_MAX
#define uintmax UINT_MAX
#define ulmax ULONG_MAX
#define llmax LLONG_MAX
#define ll long long
#define rep(i, a, N) for ((i) = (a); (i) < (N); (i)++)
#define rrp(i, N, a) for ((i) = (N)-1; (i) >= (a); (i)--)
#define llfor ll i, j
#define sc(a) cin >> a
#define pr(a) cout << a << endl
#define pY puts("YES")
#define pN puts("NO")
#define py puts("Yes")
#define pn puts("No")
#define pnn printf("\n")
#define pb(b) push_back(b)
#define all(a) a.begin(), a.end()
#define llvec vector<vector<ll>>
#define charvec vector<vector<char>>
#define size(a, b) (a, vector<ll>(b))
/*
UnionFind：素集合系管理の構造体(union by size)
isSame(x, y): x と y が同じ集合にいるか。 計算量はならし O(α(n))
unite(x, y): x と y を同じ集合にする。計算量はならし O(α(n))
treeSize(x): x を含む集合の要素数。
*/
struct UnionFind {
  vector<int> size, parents;
  UnionFind() {}
  UnionFind(int n) { // make n trees.
    size.resize(n, 0);
    parents.resize(n, 0);
    for (int i = 0; i < n; i++)
      makeTree(i);
  }
  void makeTree(int x) {
    parents[x] = x; // the parent of x is x
    size[x] = 1;
  }
  bool isSame(int x, int y) { return findRoot(x) == findRoot(y); }
  bool unite(int x, int y) {
    x = findRoot(x);
    y = findRoot(y);
    if (x == y)
      return false;
    if (size[x] > size[y]) {
      parents[y] = x;
      size[x] += size[y];
    } else {
      parents[x] = y;
      size[y] += size[x];
    }
    return true;
  }
  int findRoot(int x) { // 木の根を探す,計算量削減のため低く
    if (x != parents[x])
      parents[x] = findRoot(parents[x]);
    return parents[x];
  }
  int treeSize(int x) { return size[findRoot(x)]; }
};
/*mod*/ const int mod = 1e9 + 7;
/*pi*/ const double pi = acos(-1);
/*繰り上げ除算*/ ll cei(ll x, ll y) {
  ll ans = x / y;
  if (x % y != 0)
    ans++;
  return ans;
}
/*最大公約数*/ ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
/*最小公倍数*/ ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }
/*n乗 1*/ ll llpow(ll x, ll n) {
  ll ans = 1, i;
  rep(i, 0, n) {
    ans *= x;
    ans %= mod;
  }
  return ans;
}
/*n乗 2*/ ll modpow(ll x, ll n) {
  ll ans = x, i, tmp = x, t1 = 1;
  i = 1;
  while (i < n) {
    if (i * 2 < n) {
      ans *= ans;
      ans %= mod;
      i *= 2;
    } else {
      t1 = 1;
      tmp = x;
      while (t1 * 2 < n - i) {
        tmp *= tmp;
        tmp %= mod;
        t1 *= 2;
      }
      ans *= tmp;
      ans %= mod;
      i += t1;
    }
  }
  return ans;
}
/*階乗*/ ll fact(ll x) {
  ll i, ans = 1;
  rep(i, 0, x) {
    ans *= (x - i);
    ans %= mod;
  }
  return ans;
}
/*逆元*/ ll inv(ll x) { return modpow(x, mod - 2); }
/*nCr*/ ll ncr(ll n, ll r) {
  ll a = fact(n), b = modpow(fact(n - r), mod - 2),
     c = modpow(fact(r), mod - 2);
  ll ans = a * b;
  ans %= mod;
  ans *= c;
  ans %= mod;
  return ans;
}
/*nPr*/ ll npr(ll n, ll r) {
  ll a = fact(n), b = modpow(fact(n - r), mod - 2);
  return (a * b) % mod;
}
/*primejudge*/ bool prime(ll a) {
  if (a <= 1)
    return false;
  ll i;
  for (i = 2; i * i <= a; i++) {
    if (a % i == 0)
      return false;
  }
  return true;
}
/*Fibonacci数列*/ ll fib(ll x) {
  ll i, fibo[x + 10];
  fibo[0] = 1;
  fibo[1] = 1;
  fibo[2] = 1;
  rep(i, 3, x + 1) fibo[i] = fibo[i - 1] + fibo[i - 2];
  return fibo[x];
}
/*桁数*/ ll dig(ll n) {
  ll d = 0, tmp = n;
  while (tmp / 10 > 0) {
    tmp /= 10;
    d++;
  }
  return d;
}
/*迷路移動*/ const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
llfor; ////////////////////////////////////////////////////////////
ll n, m, q, num[20], ans;
ll a[20], b[20], c[20], d[20];
void making(ll x) {
  ll y1;
  ll st = (x == 0 ? 1 : num[x - 1]);
  rep(y1, st, m + 1) {
    num[x] = y1;
    if (x == n - 1) {
      ll cnt = 0;
      rep(i, 0, q) {
        if (num[b[i]] - num[a[i]] == c[i])
          cnt += d[i];
      }
      // rep(i,0,n)cout<<num[i]<<" ";pr(cnt);
      ans = max(ans, cnt);
    } else
      making(x + 1);
  }
}
int main() {
  cin >> n >> m >> q;
  rep(i, 0, q) {
    cin >> a[i] >> b[i] >> c[i] >> d[i];
    a[i]--;
    b[i]--;
  }
  ans = 0;
  making(0);
  pr(ans);
  return 0;
}

Fixed submission:
#include <algorithm>
#include <climits>
#include <cmath>
#include <cstring>
#include <functional>
#include <iostream>
#include <limits.h>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vector>
using namespace std;

#define intmax INT_MAX
#define lmax LONG_MAX
#define uintmax UINT_MAX
#define ulmax ULONG_MAX
#define llmax LLONG_MAX
#define ll long long
#define rep(i, a, N) for ((i) = (a); (i) < (N); (i)++)
#define rrp(i, N, a) for ((i) = (N)-1; (i) >= (a); (i)--)
#define llfor ll i, j
#define sc(a) cin >> a
#define pr(a) cout << a << endl
#define pY puts("YES")
#define pN puts("NO")
#define py puts("Yes")
#define pn puts("No")
#define pnn printf("\n")
#define pb(b) push_back(b)
#define all(a) a.begin(), a.end()
#define llvec vector<vector<ll>>
#define charvec vector<vector<char>>
#define size(a, b) (a, vector<ll>(b))
/*
UnionFind：素集合系管理の構造体(union by size)
isSame(x, y): x と y が同じ集合にいるか。 計算量はならし O(α(n))
unite(x, y): x と y を同じ集合にする。計算量はならし O(α(n))
treeSize(x): x を含む集合の要素数。
*/
struct UnionFind {
  vector<int> size, parents;
  UnionFind() {}
  UnionFind(int n) { // make n trees.
    size.resize(n, 0);
    parents.resize(n, 0);
    for (int i = 0; i < n; i++)
      makeTree(i);
  }
  void makeTree(int x) {
    parents[x] = x; // the parent of x is x
    size[x] = 1;
  }
  bool isSame(int x, int y) { return findRoot(x) == findRoot(y); }
  bool unite(int x, int y) {
    x = findRoot(x);
    y = findRoot(y);
    if (x == y)
      return false;
    if (size[x] > size[y]) {
      parents[y] = x;
      size[x] += size[y];
    } else {
      parents[x] = y;
      size[y] += size[x];
    }
    return true;
  }
  int findRoot(int x) { // 木の根を探す,計算量削減のため低く
    if (x != parents[x])
      parents[x] = findRoot(parents[x]);
    return parents[x];
  }
  int treeSize(int x) { return size[findRoot(x)]; }
};
/*mod*/ const int mod = 1e9 + 7;
/*pi*/ const double pi = acos(-1);
/*繰り上げ除算*/ ll cei(ll x, ll y) {
  ll ans = x / y;
  if (x % y != 0)
    ans++;
  return ans;
}
/*最大公約数*/ ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
/*最小公倍数*/ ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }
/*n乗 1*/ ll llpow(ll x, ll n) {
  ll ans = 1, i;
  rep(i, 0, n) {
    ans *= x;
    ans %= mod;
  }
  return ans;
}
/*n乗 2*/ ll modpow(ll x, ll n) {
  ll ans = x, i, tmp = x, t1 = 1;
  i = 1;
  while (i < n) {
    if (i * 2 < n) {
      ans *= ans;
      ans %= mod;
      i *= 2;
    } else {
      t1 = 1;
      tmp = x;
      while (t1 * 2 < n - i) {
        tmp *= tmp;
        tmp %= mod;
        t1 *= 2;
      }
      ans *= tmp;
      ans %= mod;
      i += t1;
    }
  }
  return ans;
}
/*階乗*/ ll fact(ll x) {
  ll i, ans = 1;
  rep(i, 0, x) {
    ans *= (x - i);
    ans %= mod;
  }
  return ans;
}
/*逆元*/ ll inv(ll x) { return modpow(x, mod - 2); }
/*nCr*/ ll ncr(ll n, ll r) {
  ll a = fact(n), b = modpow(fact(n - r), mod - 2),
     c = modpow(fact(r), mod - 2);
  ll ans = a * b;
  ans %= mod;
  ans *= c;
  ans %= mod;
  return ans;
}
/*nPr*/ ll npr(ll n, ll r) {
  ll a = fact(n), b = modpow(fact(n - r), mod - 2);
  return (a * b) % mod;
}
/*primejudge*/ bool prime(ll a) {
  if (a <= 1)
    return false;
  ll i;
  for (i = 2; i * i <= a; i++) {
    if (a % i == 0)
      return false;
  }
  return true;
}
/*Fibonacci数列*/ ll fib(ll x) {
  ll i, fibo[x + 10];
  fibo[0] = 1;
  fibo[1] = 1;
  fibo[2] = 1;
  rep(i, 3, x + 1) fibo[i] = fibo[i - 1] + fibo[i - 2];
  return fibo[x];
}
/*桁数*/ ll dig(ll n) {
  ll d = 0, tmp = n;
  while (tmp / 10 > 0) {
    tmp /= 10;
    d++;
  }
  return d;
}
/*迷路移動*/ const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
llfor; ////////////////////////////////////////////////////////////
ll n, m, q, num[100], ans;
ll a[100], b[100], c[100], d[100];
void making(ll x) {
  ll y1;
  ll st = (x == 0 ? 1 : num[x - 1]);
  rep(y1, st, m + 1) {
    num[x] = y1;
    if (x == n - 1) {
      ll cnt = 0;
      rep(i, 0, q) {
        if (num[b[i]] - num[a[i]] == c[i])
          cnt += d[i];
      }
      // rep(i,0,n)cout<<num[i]<<" ";pr(cnt);
      ans = max(ans, cnt);
    } else
      making(x + 1);
  }
}
int main() {
  cin >> n >> m >> q;
  rep(i, 0, q) {
    cin >> a[i] >> b[i] >> c[i] >> d[i];
    a[i]--;
    b[i]--;
  }
  ans = 0;
  making(0);
  pr(ans);
  return 0;
}