#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

struct Edge { int x, y, w; };
vector<Edge> edges;
int n, m, S, T;

int find(int x, int* parent) {
    return parent[x] == x ? x : parent[x] = find(parent[x], parent);
}

int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }

int main() {
    cin >> n >> m;
    edges.resize(m);
    for (int i = 0; i < m; ++i) 
        cin >> edges[i].x >> edges[i].y >> edges[i].w;
    cin >> S >> T;
    sort(edges.begin(), edges.end(), [](const Edge& a, const Edge& b) {
        return a.w < b.w;
    });

    int* parent = new int[n + 1];
    int ans_a = -1, ans_b = -1;
    for (int i = 0; i < m; ++i) {
        for (int k = 1; k <= n; ++k) parent[k] = k;
        for (int j = i; j < m; ++j) {
            int fx = find(edges[j].x, parent);
            int fy = find(edges[j].y, parent);
            if (fx != fy) parent[fx] = fy;
            if (find(S, parent) == find(T, parent)) {
                if (ans_a == -1 || 
                    (double)edges[j].w / edges[i].w < (double)ans_a / ans_b) {
                    ans_a = edges[j].w;
                    ans_b = edges[i].w;
                }
                break;
            }
        }
    }
    delete[] parent;

    if (ans_a == -1) cout << "IMPOSSIBLE";
    else {
        int g = gcd(ans_a, ans_b);
        ans_a /= g; ans_b /= g;
        if (ans_b == 1) cout << ans_a;
        else cout << ans_a << '/' << ans_b;
    }
    return 0;
}