#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = (n)-1; i >= 0; --i)
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T, n, m;
    cin >> T >> n >> m;
    vector<vector<P>> to(n);
    rep(_, m) {
        int u, v, w;
        cin >> u >> v >> w;
        --u, --v;
        to[u].emplace_back(v, w);
        if (T == 0) to[v].emplace_back(u, w);
    }
    constexpr ll inf = 1002003004005006007;
    ll ans = inf;
    rep(s, n) {
        VI first_move(n);
        VL dist(n, inf);
        priority_queue<P, vector<P>, greater<P>> q;
        auto push = [&](int v, ll c) {
            if (c < dist[v]) {
                first_move[v] = false;
                dist[v] = c;
                q.emplace(c, v);
            }
        };
        for(auto [v, w]: to[s]) {
            push(v, w);
            first_move[v] = true;
        }
        while(!q.empty()) {
            auto [c, u] = q.top(); q.pop();
            if (c != dist[u]) continue;
            for(auto [v, w]: to[u]) {
                if (first_move[u] && v == s) continue;
                push(v, c + w);
            }
        }
        chmin(ans, dist[s]);
    }
    if (ans == inf) ans = -1;
    cout << ans << endl;
}