#include <bits/stdc++.h>   using namespace std;   int dp[81][81][81], n, m, i, j, k, ans, inf = 1000007, x, y, l, len;   pair<int, int> p;   vector<pair<int, int> > g[82];   int main() {     cin >> n >> m;     if (m > n) {       cout << -1 << endl;       return 0;     }     cin >> k;     for (i = 0; i < k; i++) {       cin >> x >> y >> l;       if (x == y) continue;       p.first = y;       p.second = l;       g[x].push_back(p);     }     for (i = 1; i <= n; i++)       for (j = 1; j <= n; j++)         for (k = 1; k <= n; k++) dp[i][j][k] = inf;     for (i = 1; i <= n; i++)       for (j = 1; j <= n; j++) dp[i][j][1] = 0;     for (k = 2; k <= m; k++)       for (j = 1; j < n; j++)         for (i = 1; i <= n - j; i++) {           len = g[i].size();           for (l = 0; l < len; l++) {             if (g[i][l].first < i) continue;             if (g[i][l].first > i + j) continue;             dp[i][i + j][k] =                 min(dp[i][i + j][k], min(dp[g[i][l].first][i + 1][k - 1],                                          dp[g[i][l].first][i + j][k - 1]) +                                          g[i][l].second);           }           len = g[i + j].size();           for (l = 0; l < len; l++) {             if (g[i + j][l].first > i + j) continue;             if (g[i + j][l].first < i) continue;             dp[i + j][i][k] =                 min(dp[i + j][i][k], min(dp[g[i + j][l].first][i + j - 1][k - 1],                                          dp[g[i + j][l].first][i][k - 1]) +                                          g[i + j][l].second);           }         }     ans = inf;     for (i = 1; i <= n; i++)       for (j = 1; j <= n; j++) ans = min(ans, dp[i][j][m]);     if (ans == inf)       cout << -1 << endl;     else       cout << ans << endl;     return 0;   }   