#pragma GCC target ("avx2")
// #pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")

#include <iostream>
#include <array>
#include <algorithm>
#include <vector>
#include <bitset>
#include <set>
#include <unordered_set>
#include <cmath>
#include <complex>
#include <deque>
#include <iterator>
#include <numeric>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <string>
#include <tuple>
#include <utility>
#include <limits>
#include <iomanip>
#include <functional>
#include <cassert>
// #include <atcoder/all>
using namespace std;

using ll=long long;
template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;
using vll = V<ll>;
using vii = V<int>;
using vvll = V<vll>;
using vvii = V< V<int> >;
using PII = P<int, int>;
using PLL = P<ll, ll>;
#define RevREP(i,n,a) for(ll i=n;i>a;i--)  // (a,n]
#define REP(i,a,n) for(ll i=a;i<n;i++)  // [a,n)
#define rep(i, n) REP(i,0,n)
#define ALL(v) v.begin(),v.end()
#define eb emplace_back
#define pb push_back
template < class T > inline bool chmax(T& a, T b) {if (a < b) { a=b; return true; } return false; }
template < class T > inline bool chmin(T& a, T b) {if (a > b) { a=b; return true; } return false; }
#define DEBUG_VLL(vec) for(int sz=0;sz<int(vec.size());sz++) std::cerr<<vec[sz]<<(sz==int(vec.size())-1?'\n':' ');

const long long MOD = 1000000007;
const long long HIGHINF = (long long)1e18;
const int INF = (int)1e9;

using PLI = P<ll, int>;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int t, n, m; cin >> t >> n >> m;
    V< V<PII> > edges(n);
    rep(i, m) {
        int u, v, w; cin >> u >> v >> w;
        u--, v--;
        edges[u].eb(PII(v, w));
        if (t == 0) edges[v].eb(PII(u, w));
    }

    ll ans = HIGHINF;
    rep(i, n) {
        for (PII to: edges[i]) {
            auto [ton, tow] = to;
            vll dist(n, HIGHINF);
            priority_queue<PLI> pq;
            pq.push(PLI(0, ton));
            while (pq.size() > 0) {
                PLI q = pq.top(); pq.pop();
                if (dist[q.second] < -q.first) continue;
                dist[q.second] = -q.first;
                for (PII e: edges[q.second]) {
                    if (dist[e.first] < ll(-q.first) + e.second) continue;
                    if ((q.second == i and e.first == ton) or (t == 0 and q.second == ton and e.first == i)) continue;
                    pq.push(PLI(-(ll(-q.first) + e.second), e.first));
                }
            }
            if (dist[i] < HIGHINF) chmin(ans, dist[i] + tow);
        }
    }
    if (ans == HIGHINF) ans = -1;
    cout << ans << '\n';
    return 0;
}