#ifdef LOCAL
    #define _GLIBCXX_DEBUG
    #define __clock__
#else
    #pragma GCC optimize("Ofast")
    // #define NDEBUG
#endif
// #define __buffer_check__
#define __precision__ 10
#define iostream_untie true
#define debug_stream std::cerr

#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <complex>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>

#define all(v) std::begin(v), std::end(v)
#define rall(v) std::rbegin(v), std::rend(v)
#define odd(n) ((n) & 1)
#define even(n) (not __odd(n))
#define __popcount(n) __builtin_popcountll(n)
#define __clz32(n) __builtin_clz(n)
#define __clz64(n) __builtin_clzll(n)
#define __ctz32(n) __builtin_ctz(n)
#define __ctz64(n) __builtin_ctzll(n)

using i32 = int_least32_t; using i64 = int_least64_t; using u32 = uint_least32_t; using u64 = uint_least64_t;
using pii = std::pair<i32, i32>; using pll = std::pair<i64, i64>;
template <class T> using heap = std::priority_queue<T>;
template <class T> using rheap = std::priority_queue<T, std::vector<T>, std::greater<T>>;
template <class T> using hashset = std::unordered_set<T>;
template <class Key, class Value> using hashmap = std::unordered_map<Key, Value>;

namespace setting
{
    using namespace std::chrono;
    system_clock::time_point start_time, end_time;
    long long get_elapsed_time() { end_time = system_clock::now(); return duration_cast<milliseconds>(end_time - start_time).count(); }
    void print_elapsed_time() { debug_stream << "\n----- Exec time : " << get_elapsed_time() << " ms -----\n"; }
    void buffer_check() { char bufc; if(std::cin >> bufc) debug_stream << "\n\033[1;35mwarning\033[0m: buffer not empty.\n"; }
    struct setupper
    {
        setupper()
        {
            if(iostream_untie) std::ios::sync_with_stdio(false), std::cin.tie(nullptr);
            std::cout << std::fixed << std::setprecision(__precision__);
    #ifdef stderr_path
            if(freopen(stderr_path, "a", stderr))
            {
                std::cerr << std::fixed << std::setprecision(__precision__);
            }
    #endif
    #ifdef stdout_path
            if(not freopen(stdout_path, "w", stdout))
            {
                freopen("CON", "w", stdout);
                debug_stream << "\n\033[1;35mwarning\033[0m: failed to open stdout file.\n";
            }
            std::cout << "";
    #endif
    #ifdef stdin_path
            if(not freopen(stdin_path, "r", stdin))
            {
                freopen("CON", "r", stdin);
                debug_stream << "\n\033[1;35mwarning\033[0m: failed to open stdin file.\n";
            }
    #endif
    #ifdef LOCAL
            debug_stream << "\n----- stderr at LOCAL -----\n\n";
            atexit(print_elapsed_time);
    #endif
    #ifdef __buffer_check__
            atexit(buffer_check);
    #endif
    #if defined(__clock__) || defined(LOCAL)
            start_time = system_clock::now();
    #endif
        }
    } __setupper; // struct setupper
} // namespace setting
#ifdef __clock__
class
{
    std::chrono::system_clock::time_point built_pt, last_pt; int built_ln, last_ln;
    std::string built_func, last_func; bool is_built = false;
  public:
    void build(int crt_ln, const std::string &crt_func)
    {
        is_built = true, last_pt = built_pt = std::chrono::system_clock::now(), last_ln = built_ln = crt_ln, last_func = built_func = crt_func;
    }
    void set(int crt_ln, const std::string &crt_func)
    {
        if(is_built) last_pt = std::chrono::system_clock::now(), last_ln = crt_ln, last_func = crt_func;
        else debug_stream << "[ " << crt_ln << " : " << crt_func << " ] " << "myclock_t::set failed (yet to be built!)\n";
    }
    void get(int crt_ln, const std::string &crt_func)
    {
        if(is_built)
        {
            std::chrono::system_clock::time_point crt_pt(std::chrono::system_clock::now());
            long long diff = std::chrono::duration_cast<std::chrono::milliseconds>(crt_pt - last_pt).count();
            debug_stream << diff << " ms elapsed from" << " [ " << last_ln << " : " << last_func << " ]";
            if(last_ln == built_ln) debug_stream << " (when built)";
            debug_stream << " to" << " [ " << crt_ln << " : " << crt_func << " ]" << "\n";
            last_pt = built_pt, last_ln = built_ln, last_func = built_func;
        }
        else
        {
            debug_stream << "[ " << crt_ln << " : " << crt_func << " ] " << "myclock_t::get failed (yet to be built!)\n";
        }
    }
} myclock; // unnamed class
    #define build_clock() myclock.build(__LINE__, __func__)
    #define set_clock() myclock.set(__LINE__, __func__)
    #define get_clock() myclock.get(__LINE__, __func__)
#else
    #define build_clock() ((void)0)
    #define set_clock() ((void)0)
    #define get_clock() ((void)0)
#endif

namespace std
{
    // hash
    template <class T> size_t hash_combine(size_t seed, T const &key) { return seed ^ (hash<T>()(key) + 0x9e3779b9 + (seed << 6) + (seed >> 2)); }
    template <class T, class U> struct hash<pair<T, U>> { size_t operator()(pair<T, U> const &pr) const { return hash_combine(hash_combine(0, pr.first), pr.second); } };
    template <class tuple_t, size_t index = tuple_size<tuple_t>::value - 1> struct tuple_hash_calc { static size_t apply(size_t seed, tuple_t const &t) { return hash_combine(tuple_hash_calc<tuple_t, index - 1>::apply(seed, t), get<index>(t)); } };
    template <class tuple_t> struct tuple_hash_calc<tuple_t, 0> { static size_t apply(size_t seed, tuple_t const &t) { return hash_combine(seed, get<0>(t)); } };
    template <class... T> struct hash<tuple<T...>> { size_t operator()(tuple<T...> const &t) const { return tuple_hash_calc<tuple<T...>>::apply(0, t); } };
    // iostream
    template <class T, class U> istream &operator>>(istream &is, pair<T, U> &p) { return is >> p.first >> p.second; }
    template <class T, class U> ostream &operator<<(ostream &os, const pair<T, U> &p) { return os << p.first << ' ' << p.second; }
    template <class tuple_t, size_t index> struct tupleis { static istream &apply(istream &is, tuple_t &t) { tupleis<tuple_t, index - 1>::apply(is, t); return is >> get<index>(t); } };
    template <class tuple_t> struct tupleis<tuple_t, SIZE_MAX> { static istream &apply(istream &is, tuple_t &t) { return is; } };
    template <class... T> istream &operator>>(istream &is, tuple<T...> &t) { return tupleis<tuple<T...>, tuple_size<tuple<T...>>::value - 1>::apply(is, t); }
    template <> istream &operator>>(istream &is, tuple<> &t) { return is; }
    template <class tuple_t, size_t index> struct tupleos { static ostream &apply(ostream &os, const tuple_t &t) { tupleos<tuple_t, index - 1>::apply(os, t); return os << ' ' << get<index>(t); } };
    template <class tuple_t> struct tupleos<tuple_t, 0> { static ostream &apply(ostream &os, const tuple_t &t) { return os << get<0>(t); } };
    template <class... T> ostream &operator<<(ostream &os, const tuple<T...> &t) { return tupleos<tuple<T...>, tuple_size<tuple<T...>>::value - 1>::apply(os, t); }
    template <> ostream &operator<<(ostream &os, const tuple<> &t) { return os; }
    template <class Container, typename Value = typename Container::value_type, enable_if_t<!is_same<decay_t<Container>, string>::value, nullptr_t> = nullptr>
    istream& operator>>(istream& is, Container &cont) { for(auto&& e : cont) is >> e; return is; }
    template <class Container, typename Value = typename Container::value_type, enable_if_t<!is_same<decay_t<Container>, string>::value, nullptr_t> = nullptr>
    ostream& operator<<(ostream& os, const Container &cont) { bool flag = 1; for(auto&& e : cont) flag ? flag = 0 : (os << ' ', 0), os << e; return os; }
} // namespace std

#ifdef LOCAL
    #define dump(...)                                                              \
        debug_stream << "[ " << __LINE__ << " : " << __FUNCTION__ << " ]\n",       \
            dump_func(#__VA_ARGS__, __VA_ARGS__)
    template <class T> void dump_func(const char *ptr, const T &x)
    {
        debug_stream << '\t';
        for(char c = *ptr; c != '\0'; c = *++ptr) if(c != ' ') debug_stream << c;
        debug_stream << " : " << x << '\n';
    }
    template <class T, class... rest_t> void dump_func(const char *ptr, const T &x, rest_t... rest)
    {
        debug_stream << '\t';
        for(char c = *ptr; c != ','; c = *++ptr) if(c != ' ') debug_stream << c;
        debug_stream << " : " << x << ",\n"; dump_func(++ptr, rest...);
    }
#else
    #define dump(...) ((void)0)
#endif

template <class T = int> T read() { T x; std::cin >> x; return x; }
template <class iterator> void read(iterator __first, iterator __last) { for(iterator i = __first; i != __last; ++i) std::cin >> *i; }
template <class iterator> void write(iterator __first, iterator __last) { for(iterator i = __first; i != __last; std::cout << (++i == __last ? "" : " ")) std::cout << *i; }

// substitute y for x if x > y.
template <class T> inline bool sbmin(T &x, const T &y) { return x > y ? x = y, true : false; }
// substitute y for x if x < y.
template <class T> inline bool sbmax(T &x, const T &y) { return x < y ? x = y, true : false; }

// binary search on integers.
long long bin(long long __ok, long long __ng, const std::function<bool(long long)> &pred)
{
    while(std::abs(__ok - __ng) > 1)
    {
        long long mid{(__ok + __ng) / 2};
        (pred(mid) ? __ok : __ng) = mid;
    }
    return __ok;
}
// binary search on real numbers.
long double bin(long double __ok, long double __ng, const long double eps, const std::function<bool(long double)> &pred)
{
    while(std::abs(__ok - __ng) > eps)
    {
        long double mid{(__ok + __ng) / 2};
        (pred(mid) ? __ok : __ng) = mid;
    }
    return __ok;
}
// binary search on integers(with a class member function).
template <class X, class int_t>
long long bin(long long __ok, long long __ng, bool (X::*const pred)(int_t), X *const x)
{
    while(std::abs(__ok - __ng) > 1)
    {
        long long mid{(__ok + __ng) / 2};
        ((x->*pred)(mid) ? __ok : __ng) = mid;
    }
    return __ok;
}
// binary search on real numbers(with a class member function).
template <class X, class real_t>
long double bin(long double __ok, long double __ng, const long double eps, bool (X::*const pred)(real_t), X *const x)
{
    while(std::abs(__ok - __ng) > eps)
    {
        long double mid{(__ok + __ng) / 2};
        ((x->*pred)(mid) ? __ok : __ng) = mid;
    }
    return __ok;
}

// be careful that val is type-sensitive.
template <class T, class A, size_t N> void init(A (&array)[N], const T &val) { std::fill((T*)array, (T*)(array + N), val); }

// reset all bits.
template <class A> void reset(A &array) { memset(array, 0, sizeof(array)); }


/* The main code follows. */

using namespace std;

// Base class
template <class cap_t, class cost_t>
struct Flow
{
    struct edge_t
    {
        size_t from, to; cap_t cap; cost_t cost; size_t rev;
        edge_t(size_t _from, size_t _to, cap_t _cap, cost_t _cost, size_t _rev) : from(_from), to(_to), cap(_cap), cost(_cost), rev(_rev) {}
    }; // struct edge_t

  protected:
    size_t V;
    std::vector<std::vector<edge_t>> adj;

  public:
    Flow(size_t _V) : V(_V), adj(_V) {}

    size_t size() const { return V; }
    std::vector<edge_t> &operator[](size_t v) { return adj[v]; }

    void add_edge(size_t from, size_t to, cap_t cap, cost_t cost)
    {
        adj[from].emplace_back(from, to, cap, cost, adj[to].size());
        adj[to].emplace_back(to, from, 0, -cost, adj[from].size() - 1);
    }
}; // struct Flow

template <class cap_t>
class Dinic : public Flow<cap_t, cap_t>
{
    using Base = Flow<cap_t, cap_t>;
    // using edge_t = typename Base::edge_t;
    // using Base::adj;

    std::vector<size_t> level, itr;

    bool bfs(size_t s, size_t t)
    {
        fill(level.begin(), level.end(), ~0);
        std::queue<size_t> que;
        que.emplace(s);
        level[s] = 0;
        while(!que.empty())
        {
            size_t v = que.front(); que.pop();
            for(const typename Base::edge_t &e : Base::adj[v])
            {
                if(e.cap > cap_t(0) && not ~level[e.to])
                {
                    level[e.to] = level[v] + 1;
                    que.emplace(e.to);
                }
            }
        }
        return ~level[t];
    }

    cap_t dfs(size_t v, size_t t, cap_t f)
    {
        if(v == t) return f;
        cap_t res(0);
        while(itr[v] < Base::adj[v].size())
        {
            typename Base::edge_t &e = Base::adj[v][itr[v]];
            if(e.cap > cap_t(0) && level[v] < level[e.to])
            {
                cap_t d = dfs(e.to, t, std::min(f, e.cap));
                e.cap -= d;
                Base::adj[e.to][e.rev].cap += d;
                res += d;
                if((f -= d) == cap_t(0)) break;
            }
            ++itr[v];
        }
        return res;
    }

  public:
    Dinic(size_t V) : Base::Flow(V), level(V), itr(V) {}

    void add_edge(size_t s, size_t t, cap_t cap) { Base::add_edge(s, t, cap, 0); }

    cap_t max_flow(size_t s, size_t t)
    {
        cap_t res = 0, f;
        while(bfs(s, t))
        {
            fill(itr.begin(), itr.end(), 0);
            while((f = dfs(s, t, std::numeric_limits<cap_t>::max())) > cap_t(0)) res += f;
        }
        return res;
    }

    class cut_t
    {
        size_t V; bool* const data;
        friend class Dinic;
      public:
        cut_t(size_t _V) : V(_V), data(new bool[V]()) {}
        ~cut_t() { delete[] data; }

        size_t size() const { return V; }
        bool &operator[](size_t v) const { return data[v]; }
        bool *begin() const { return data; }
        bool *end() const { return data + V; }
        friend std::ostream &operator<<(std::ostream &s, const cut_t &cut)
        {
            bool is_front = true;
            for(bool b : cut)
            {
                if(is_front) is_front = false;
                else s << ' ';
                s << b;
            }
            return s;
        }
    }; // class cut_t

    cut_t min_cut(size_t s, size_t t)
    {
        while(bfs(s, t))
        {
            fill(itr.begin(), itr.end(), 0);
            while(dfs(s, t, std::numeric_limits<cap_t>::max()) > cap_t(0));
        }
        cut_t res(Base::V);
        for(size_t v = 0; v != Base::V; ++v) if(~level[v]) res.data[v] = 1;
        return res;
    }
}; // class Dinic


struct solver
{

    solver()
    {
        const int inf=2e8;

        int n,m,s,t; cin>>n>>m>>s>>t;
        --s,--t;

        int d[222][222],c[222][222];
        init(d,inf);
        init(c,inf);
        for(int i=0; i<n; ++i) d[i][i]=0;
        for(int i=0; i<m; ++i)
        {
            int u,v,_d,_c; cin>>u>>v>>_d>>_c;
            --u,--v;
            sbmin(d[u][v],_d);
            sbmin(c[u][v],_c);
        }

        int dist_s[222],dist_t[222];

        {
            bool used[222]={};
            auto &dist=dist_s;
            init(dist,inf);
            dist[s]=0;
            for(int c=0; c<n; ++c)
            {
                int nxv=-1;
                int nxd=inf;
                for(int v=0; v<n; ++v)
                {
                    if(!used[v] and sbmin(nxd,dist[v]))
                    {
                        nxv=v;
                    }
                }
                used[nxv]=true;
                for(int v=0; v<n; ++v)
                {
                    sbmin(dist[v],nxd+d[nxv][v]);
                }
            }
        }

        {
            bool used[222]={};
            auto &dist=dist_t;
            init(dist,inf);
            dist[t]=0;
            for(int c=0; c<n; ++c)
            {
                int nxv=-1;
                int nxd=inf;
                for(int v=0; v<n; ++v)
                {
                    if(!used[v] and sbmin(nxd,dist[v]))
                    {
                        nxv=v;
                    }
                }
                used[nxv]=true;
                for(int v=0; v<n; ++v)
                {
                    sbmin(dist[v],nxd+d[v][nxv]);
                }
            }
        }

        const int minpath=dist_s[t];
        assert(minpath==dist_t[s]);
        dump(minpath);

        Dinic<int> flow(n);

        for(int i=0; i<n; ++i)
        {
            for(int j=0; j<n; ++j)
            {
                if(dist_s[i]+dist_t[j]+d[i][j]==minpath)
                {
                    dump(i,j);
                    flow.add_edge(i,j,c[i][j]);
                }
            }
        }

        cout << flow.max_flow(s,t) << "\n";
    }
}; // struct solver


int main(int argc, char *argv[])
{
    u32 t; // loop count
#ifdef LOCAL
    t = 1;
#else
    t = 1; // single test case
#endif
    // t = -1; // infinite loop
    // cin >> t; // case number given

    while(t--)
    {
        solver();
    }
}



Measured memory_bytes: 3692