#include <bits/stdc++.h>   using namespace std;   const int N = 81;   const int M = 2001;   int n, k, m, ans = 1e9;   int cache[N][2][N][N];   vector<pair<int, int> > g[N];   int dp(int idx, int dir, int dist, int taken) {     if (taken == k) return 0;     int &ans = cache[idx][dir][dist][taken];     if (ans != -1) return ans;     ans = 1e9;     for (auto &it : g[idx]) {       if (abs(it.first - idx) <= dist) {         if ((it.first - idx > 0 && dir > 0) || (idx - it.first > 0 && dir == 0)) {           ans = min(               ans,               it.second +                   min(dp(it.first, dir, dist - abs(it.first - idx), taken + 1),                       dp(it.first, dir ^ 1, abs(it.first - idx) - 1, taken + 1)));         }       }     }     return ans;   }   int32_t main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     ;     memset(cache, -1, sizeof(cache));     cin >> n >> k >> m;     for (int i = 1; i <= m; i++) {       int u, v, c;       cin >> u >> v >> c;       g[u].push_back({v, c});     }     for (int i = 1; i <= n; i++)       ans = min(ans, min(dp(i, 1, n - i, 1), dp(i, 0, i - 1, 1)));     if (ans > 1e8) ans = -1;     cout << ans;     return 0;   }   