#include  "iostream"
#include "vector"
using namespace std;
int in_degree[101]; /* 记录图的各个节点的入度 */
struct Node {
    int e;
    int cost;
};
vector<Node>v[101];
int early[101];
int n, m;
bool toplogicSort() {
    int start = -1;
    for (int i = 0; i < n; i++) {
        if (in_degree[i] == 0) {
            start = i;
            break;
        }
    }
    if (start == -1) { /* 没有入度为0的点 完不成项目*/
        return false;
    }
    early[start] = 0;
    int sum = 0;
    int num = 0;
    int newP = start;
    while (num != n - 1) {
        int len = v[newP].size(); /* 出度 */
        for (int i = 0; i < len; i++) {
            int e = v[newP][i].e;
            int cost = v[newP][i].cost;
            in_degree[e]--;
            if (early[newP] + cost > early[e]) {
                early[e] = early[newP] + cost;
            }
        }
        in_degree[newP] = -1; /* 删除该节点 */
        newP = -1;
        for (int i = 0; i < n; i++) {
            if (in_degree[i] == 0) {
                newP = i;
                break;
            }
        }
        if (newP == -1)
            return false;
        if (early[newP] > sum)
            sum = early[newP];
        num++;
    }
    cout << sum << endl;
    return true;
}
int main() {
    Node node;
    cin >> n >> m;
    for(int i = 0; i < n; i++){
    in_degree[i] = 0;
    early[i] = 0;
    }
    while (m--) {
        int s, e, l;
        cin >> s >> e >> l;
        node.e = e;
        node.cost = l;
        v[s].push_back(node);
        in_degree[e]++;
    }
    if (!toplogicSort())
        cout << "Impossible" << endl;
}