#include <bits/stdc++.h>

using namespace std;

vector<bool> u;
vector<vector<pair<int, int>>> g;
void dfs(int v){
    u[v] = true;
    for (pair<int, int>&p : g[v]){
        if (!u[p.first])
            dfs(p.first);
    }
}


int main() {
    const int INF = 1e9;
    int n, m;
    cin >> n >> m;
    g.resize(n); u.resize(n);
    int f, t, w;
    for (int i = 0; i < m; ++i) {
        cin >> f >> t >> w;
        f--;
        t--;
        g[f].push_back({t, w});
    }
    vector<int> d(n, -INF);
    vector<int> tmp;
    d[0] = 0;
    for (int k = 0; k < n; ++k) {
        for (int i = 0; i <n ;++i){
            for (pair<int, int> &p : g[i]){
                if (d[i] != -INF && d[p.first] < d[i] + p.second){
                    d[p.first] = d[i] + p.second;
                    if (k == n-1)
                        tmp.push_back(p.first);
                }
            }
        }
    }
    for (int i = 0; i < tmp.size(); ++i)
        dfs(tmp[i]);
    if (u[n-1]) cout << ":)";
    else if (d[n-1] == -INF) cout << ":(";
    else cout << d[n-1];
    return 0;
}