#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;

struct d {
    int c = -10001;
};

vector<int> color;
vector<unordered_set<int>> g;
unordered_map<int, unordered_map<int, d>> cost;

int ans = 0;

bool dfs(int u, int n) {
    color[u] = 1;
    if (u == n) {
        return false;
    }
    for (auto v : g[u]) {
        if (color[v] == 0) {
            ans += cost[u][v].c;
            return dfs(v, n);
        }
        else if (color[v] == 1 && v != u) {
            return true;
        }
    }
    color[u] = 2;
    return false;
}

void solve() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int n, m;
    cin >> n >> m;
    g.resize(n);
    color.resize(n);

    for (int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        --a, --b;
        if (a != b) {
            g[a].insert(b);
            cost[a][b].c = max(cost[a][b].c, c);
        }
    }
    if (dfs(0, n - 1)) {
        cout << ":)"/* << ans*/;
    }
    else {
        cout << ans;
    }
}

int main() {
    solve();
    return 0;
}