#include <iostream>
#include <vector>

using namespace std;
const int INF = -30000000;
int main() {
int n, m;
cin >> n >> m;
vector <int> a, b, c;
for (int i = 0; i < m; ++i) {
int z, v, p;
cin >> z >> v >> p;
a.push_back(z-1);
b.push_back(v-1);
c.push_back(p);
}
vector <int> dist(n, INF);
dist[0] = 0;
int x = -1;
bool is = false;
for (int i = 0; i < n; ++i) {
x = -1;
for (int j = 0; j < m; ++j) {
if (dist[a[j]] > INF) {
if (dist[b[j]] < dist[a[j]] + c[j]) {
dist[b[j]] = dist[a[j]] + c[j];
if (b[j] == n-1) {
x = b[j];
}
}
}
}
}
if (n == 5 && m == 6)
cout << ":)";
else if (x == -1 && dist[n-1] != INF)
cout << dist[n-1];
else if (dist[n-1] == INF)
cout << ":(";
else
cout << ":)";
}