#include <bits/stdc++.h>

using namespace std;

const int MOD = 1000000007; // 998244353; // 998244853;

template <typename T>
struct modular {
    constexpr modular() : val(0){}
    constexpr modular(const modular<T>& _m) : val(_m.val) {}
    template <typename U> constexpr modular(const U& _r = U()) {
        val = -MOD <= _r && _r < MOD ? _r: _r % MOD;
        if (val < 0) { val += MOD; } }
    const T operator()() { return val; }
    template <typename U> explicit operator U() const { return static_cast<U>(val); }
    modular<T>& operator+=(const modular<T>& _m) { if ((val += _m.val) >= MOD) { val -= MOD; } return *this; }
    modular<T>& operator-=(const modular<T>& _m) { if ((val -= _m.val) < 0) { val += MOD; } return *this; }
    modular<T>& operator*=(const modular<T>& _m) { val = modular<T>(static_cast<int64_t>(val) * static_cast<int64_t>(_m.val)).val; return *this; }
    modular<T>& operator/=(const modular<T>& _m) {
        T a = _m.val, b = MOD, u = 0, v = 1;
        while (a != 0) {
            T q = b / a;
            b -= q * a; swap(a, b);
            u -= q * v; swap(u, v); 
        } return *this *= u; }
    modular<T>& operator =(const modular<T>& _m) { val = _m.val; return *this; }
    template <typename U> modular<T>& operator+=(const U& _r) { return *this += modular<T>(_r); }
    template <typename U> modular<T>& operator-=(const U& _r) { return *this -= modular<T>(_r); }
    template <typename U> modular<T>& operator*=(const U& _r) { return *this *= modular<T>(_r); }
    template <typename U> modular<T>& operator/=(const U& _r) { return *this /= modular<T>(_r); } 
    template <typename U> modular<T>& operator =(const U& _r) { val = modular<T>(_r).val; return *this; }
    modular<T> operator-() { return modular<T>(-val); }    
    template <typename U> friend bool operator==(const modular<U>&, const modular<U>&);
    friend std::istream& operator>>(std::istream& os, modular<T>& _m) { os >> _m.val; _m *= 1; return os; }
    friend std::ostream& operator<<(std::ostream& os, const modular<T>& _m) { return os << _m.val; }
    template <typename U>
    modular<T> exp(U e) {
        modular<T> res = 1;
        modular<T> b = val;
        if (e < 0) { b = 1/b; e *= -1; }
        for (; e; e >>= 1) {
            if (e & 1) { res *= b; }
            b *= b;
        } return res; }
private:
    T val;
};
template <typename T> inline modular<T> operator+(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) += _rhs; }
template <typename T, typename U> inline modular<T> operator+(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) += _rhs; }
template <typename T, typename U> inline modular<T> operator+(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) += _rhs; }
template <typename T> inline modular<T> operator-(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) -= _rhs; }
template <typename T, typename U> inline modular<T> operator-(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) -= _rhs; }
template <typename T, typename U> inline modular<T> operator-(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) -= _rhs; }
template <typename T> inline modular<T> operator*(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) *= _rhs; }
template <typename T, typename U> inline modular<T> operator*(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) *= _rhs; }
template <typename T, typename U> inline modular<T> operator*(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) *= _rhs; }
template <typename T> inline modular<T> operator/(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) /= _rhs; }
template <typename T, typename U> inline modular<T> operator/(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) /= _rhs; }
template <typename T, typename U> inline modular<T> operator/(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) /= _rhs; }
template <typename T> inline bool operator==(const modular<T>& _lhs, const modular<T>& _rhs) { return _lhs.val == _rhs.val; }
template <typename T, typename U> inline bool operator==(const modular<T>& _lhs, const U& _rhs) { return _lhs == modular<T>(_rhs); }
template <typename T, typename U> inline bool operator==(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) == _rhs; }
template <typename T> inline bool operator!=(const modular<T>& _lhs, const modular<T>& _rhs) { return !(_lhs == _rhs); }
template <typename T, typename U> inline bool operator!=(const modular<T>& _lhs, const U& _rhs) { return !(_lhs == _rhs); }
template <typename T, typename U> inline bool operator!=(const U& _lhs, const modular<T>& _rhs) { return !(_lhs == _rhs); }
typedef modular<int> mint;

using ll=long long ;
struct Graph {
    struct Edge {
        int u, v;
        int cost;
        Edge(int _u, int _v, int _cost) : u(_u), v(_v), cost(_cost) {}
    };
    int n, m;
    bool is_digraph;
    vector<vector<int>> g;
    vector<Edge> e;

    Graph(int _n) : n(_n), m(0) {
        assert(n >= 1);
        g.resize(n);
        set_di(false);
    }
    Graph(int _n, int _m, bool _di=false) : n(_n) {
        assert(n >= 1);
        g.resize(n);
        e.reserve(_m);
        m = 0;
        set_di(_di);
        input(_m);
    }
    void set_di(bool _di) {
        is_digraph = _di;
    }
    inline void add(int u, int v, int cost=1) {
        assert(0 <= u && u < n);
        assert(0 <= v && v < n);
        if (is_digraph) {
            //outdeg[u]++; indeg[v]++;
            g[u].emplace_back(m);

        } else {
            //deg[u]++; deg[v]++;
            g[u].emplace_back(m);
            g[v].emplace_back(m);
        }
        e.emplace_back(u, v, cost);
        m++;
    }
    void input(int _m) {
        int u, v, c;
        for (int i = 0; i < _m; i++) {
            cin >> u >> v >> c;
            u--; v--; // input 1-based
            add(u, v, c);
        }
    }
    template <typename T=int>
    vector<T> dijkstra(int s, vector<mint>& dp);

    vector<mint> ways(const vector<ll>& d, int s) {
        assert(d[s] == 0);
        vector<int> id(n);
        iota(id.begin(), id.end(), 0);
        sort(id.begin(), id.end(), [&](auto& u, auto& v){
            return d[u] < d[v];
        });
        vector<mint> dp(n, 0);
        dp[s] = 1;
        for (int v: id) {
            if (v == s) continue;
            for (int i: g[v]) {
                int u = e[i].u^e[i].v^v;
                if (d[u]+e[i].cost == d[v]) {
                    dp[v] += dp[u];
                }
            }
        }
        return dp;
    }
};
// single source shortest path
template <typename T>
vector<T> Graph::dijkstra(int s, vector<mint>& dp) {
    // modify T's INF
    //const int INF = 0x3f3f3f3f;
    const long long INF = 0x3f3f3f3f3f3f3f3f;
    vector<bool> trk(n, false);
    vector<T> d(n, INF);
    d[s] = 0;
    dp[s] = 1;
    auto comp = [&](int x, int y){
        return d[x] > d[y];
    };
    //priority_queue<int, vector<int>, decltype(comp)> pq(comp);
    using pi=pair<ll, int> ;
    priority_queue<pi, vector<pi>, greater<pi>>  pq;
    pq.push({0, s});
    while (!pq.empty()) {
        ll dis; int u;
        tie(dis, u)= pq.top();
        pq.pop();
        if (trk[u])
            continue;
        trk[u] = true;
        for (int i: g[u]) {
            int v = e[i].u ^ e[i].v ^ u;
            if (d[v] > d[u] + e[i].cost) {
                d[v] = d[u] + e[i].cost;
                pq.push({d[v], v});
                dp[v] = dp[u];
            }else if (d[v] == d[u]+e[i].cost) {
                dp[v] += dp[u];
            }
        }
    }
    return d;
}

void solve() {
    int n,m;
    cin >> n >> m;
    int s,t;
    cin >> s >> t;
    s--; t--;
    Graph g(n, m);

    vector<mint> dps(n,0), dpt(n,0);
    auto ds = g.dijkstra<ll>(s, dps);
    auto dt = g.dijkstra<ll>(t, dpt);

    //auto dps = g.ways(ds, s);
    //auto dpt = g.ways(dt, t);

    assert(ds[t] == dt[s]);
    //assert(dps[t] == dpt[s]);
    mint res = dps[t] * dpt[s];
    ll dist = ds[t];
    if (dist%2ll==0) {
        for (int i = 0; i < n; i++) {
            if (ds[i]+dt[i] == dist && ds[i]*2ll == dist)
                res -= dps[i]*dps[i] * dpt[i]*dpt[i];
        }
    }
    for (auto& p: g.e) {
        int u=p.u, v=p.v, c=p.cost;
        for (int _ = 0; _ < 2; _++) {
            if (ds[u] + c + dt[v] == dist && ds[u]*2ll < dist && dt[v]*2ll < dist)
                res -= dps[u]*dps[u] * dpt[v]*dpt[v];
            swap(u,v);
        }
    }
    cout << res;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    solve();
    cout << endl;
}


Measured memory_bytes: 14804