#include <bits/stdc++.h>
// created [2020/03/09] 22:43:41
#pragma GCC diagnostic ignored "-Wsign-compare"
#pragma GCC diagnostic ignored "-Wsign-conversion"

using i32   = int32_t;
using i64   = int64_t;
using u32   = uint32_t;
using u64   = uint64_t;
using uint  = unsigned int;
using usize = std::size_t;
using ll    = long long;
using ull   = unsigned long long;
using ld    = long double;
template<typename T, usize n>
using arr = T (&)[n];
template<typename T, usize n>
using c_arr = const T (&)[n];
template<typename T>
using max_heap = std::priority_queue<T>;
template<typename T>
using min_heap = std::priority_queue<T, std::vector<T>, std::greater<T>>;
template<typename T> constexpr T popcount(const T u) { return u ? static_cast<T>(__builtin_popcountll(static_cast<u64>(u))) : static_cast<T>(0); }
template<typename T> constexpr T log2p1(const T u) { return u ? static_cast<T>(64 - __builtin_clzll(static_cast<u64>(u))) : static_cast<T>(0); }
template<typename T> constexpr T msbp1(const T u) { return log2p1(u); }
template<typename T> constexpr T lsbp1(const T u) { return __builtin_ffsll(u); }
template<typename T> constexpr T clog(const T u) { return u ? log2p1(u - 1) : static_cast<T>(u); }
template<typename T> constexpr bool ispow2(const T u) { return u and (static_cast<u64>(u) & static_cast<u64>(u - 1)) == 0; }
template<typename T> constexpr T ceil2(const T u) { return static_cast<T>(1) << clog(u); }
template<typename T> constexpr T floor2(const T u) { return u == 0 ? static_cast<T>(0) : static_cast<T>(1) << (log2p1(u) - 1); }
template<typename T> constexpr bool btest(const T mask, const usize ind) { return static_cast<bool>((static_cast<u64>(mask) >> ind) & static_cast<u64>(1)); }
template<typename T> void bset(T& mask, const usize ind) { mask |= (static_cast<T>(1) << ind); }
template<typename T> void breset(T& mask, const usize ind) { mask &= ~(static_cast<T>(1) << ind); }
template<typename T> void bflip(T& mask, const usize ind) { mask ^= (static_cast<T>(1) << ind); }
template<typename T> void bset(T& mask, const usize ind, const bool b) { (b ? bset(mask, ind) : breset(mask, ind)); }
template<typename T> constexpr T bcut(const T mask, const usize ind) { return ind == 0 ? static_cast<T>(0) : static_cast<T>((static_cast<u64>(mask) << (64 - ind)) >> (64 - ind)); }
template<typename T> bool chmin(T& a, const T& b) { return (a > b ? a = b, true : false); }
template<typename T> bool chmax(T& a, const T& b) { return (a < b ? a = b, true : false); }
constexpr unsigned int mod                  = 1000000007;
template<typename T> constexpr T inf_v      = std::numeric_limits<T>::max() / 4;
template<typename Real> constexpr Real pi_v = Real{3.141592653589793238462643383279502884};
auto mfp = [](auto&& f) { return [=](auto&&... args) { return f(f, std::forward<decltype(args)>(args)...); }; };

template<typename T>
T in()
{
    T v;
    return std::cin >> v, v;
}
template<typename T, typename Uint, usize n, usize i>
T in_v(typename std::enable_if<(i == n), c_arr<Uint, n>>::type) { return in<T>(); }
template<typename T, typename Uint, usize n, usize i>
auto in_v(typename std::enable_if<(i < n), c_arr<Uint, n>>::type& szs)
{
    const usize s = (usize)szs[i];
    std::vector<decltype(in_v<T, Uint, n, i + 1>(szs))> ans(s);
    for (usize j = 0; j < s; j++) { ans[j] = in_v<T, Uint, n, i + 1>(szs); }
    return ans;
}
template<typename T, typename Uint, usize n>
auto in_v(c_arr<Uint, n> szs) { return in_v<T, Uint, n, 0>(szs); }
template<typename... Types>
auto in_t() { return std::tuple<std::decay_t<Types>...>{in<Types>()...}; }
struct io_init
{
    io_init()
    {
        std::cin.tie(nullptr), std::ios::sync_with_stdio(false);
        std::cout << std::fixed << std::setprecision(20);
    }
    void clear()
    {
        std::cin.tie(), std::ios::sync_with_stdio(true);
    }
} io_setting;

int out() { return 0; }
template<typename T>
int out(const T& v) { return std::cout << v, 0; }
template<typename T>
int out(const std::vector<T>& v)
{
    for (usize i = 0; i < v.size(); i++) {
        if (i > 0) { std::cout << ' '; }
        out(v[i]);
    }
    return 0;
}
template<typename T1, typename T2>
int out(const std::pair<T1, T2>& v) { return out(v.first), std::cout << ' ', out(v.second), 0; }
template<typename T, typename... Args>
int out(const T& v, const Args... args) { return out(v), std::cout << ' ', out(args...), 0; }
template<typename... Args>
int outln(const Args... args) { return out(args...), std::cout << '\n', 0; }
template<typename... Args>
int outel(const Args... args) { return out(args...), std::cout << std::endl, 0; }
#    define SHOW(...) static_cast<void>(0)
constexpr ull TEN(const usize n) { return n == 0 ? 1ULL : TEN(n - 1) * 10ULL; }

template<typename T, typename Uint, usize n, usize i>
auto make_v(typename std::enable_if<(i == n), c_arr<Uint, n>>::type, const T& v = T{}) { return v; }
template<typename T, typename Uint, usize n, usize i>
auto make_v(typename std::enable_if<(i < n), c_arr<Uint, n>>::type szs, const T& v = T{})
{
    const usize s = (usize)szs[i];
    return std::vector<decltype(make_v<T, Uint, n, i + 1>(szs, v))>(s, make_v<T, Uint, n, i + 1>(szs, v));
}
template<typename T, typename Uint, usize n>
auto make_v(c_arr<Uint, n> szs, const T& t = T{}) { return make_v<T, Uint, n, 0>(szs, t); }

template<typename Cost = usize>
struct edge
{
    using cost_type = Cost;
    usize u, v;
    Cost c;
    edge(const usize u, const usize v) : u{u}, v{v}, c{1} {}
    edge(const usize u, const usize v, const Cost& c) : u{u}, v{v}, c{c} {}
    operator usize() const { return v; }
    usize from() const { return u; }
    usize to() const { return v; }
    Cost cost() const { return c; }
    friend std::ostream& operator<<(std::ostream& os, const edge& e) { return os << e.u << "->" << e.v << ":" << e.c; }
};
template<typename Edge>
class base_graph
{
public:
    base_graph(const usize n) : v{n}, es(n), res(n) {}
    void add_edge(const usize u, const usize v, const bool bi = false)
    {
        es[u].emplace_back(u, v), res[v].emplace_back(v, u);
        if (bi) { es[v].emplace_back(v, u), res[u].emplace_back(u, v); }
    }
    template<typename Cost>
    void add_edge(const usize u, const usize v, const Cost& c, const bool bi = false)
    {
        es[u].emplace_back(u, v, c), res[v].emplace_back(v, u, c);
        if (bi) { es[v].emplace_back(v, u, c), res[u].emplace_back(u, v, c); }
    }
    std::vector<Edge>& operator[](const usize u) { return es[u]; }
    const std::vector<Edge>& operator[](const usize u) const { return es[u]; }
    std::vector<Edge>& from(const usize u) { return es[u]; }
    const std::vector<Edge>& from(const usize u) const { return es[u]; }
    std::vector<Edge>& to(const usize v) { return res[v]; }
    const std::vector<Edge>& to(const usize v) const { return res[v]; }
    usize size() const { return v; }
    friend std::ostream& operator<<(std::ostream& os, const base_graph& g)
    {
        for (usize i = 0; i < g.v; i++) {
            for (const auto& e : g.es[i]) { os << e << '\n'; }
        }
        return os;
    }

private:
    usize v;
    std::vector<std::vector<Edge>> es, res;
};
template<typename Edge>
using base_tree = base_graph<Edge>;
using graph     = base_graph<edge<>>;
using tree      = base_graph<edge<>>;
template<typename Cost>
using cost_graph = base_graph<edge<Cost>>;
template<typename Cost>
using cost_tree = base_graph<edge<Cost>>;
int main()
{
    while (true) {
        auto N = in<int>(), M = in<int>();
        if (N == 0 and M == 0) { break; }
        std::vector<int> ds(N, 0), es(N, 0);
        es[0] = 0, es[N - 1] = 1000;
        std::vector<std::vector<int>> vss(1001);
        std::vector<std::map<int, int>> mps(1001);
        cost_graph<int> fg(N), bg(N);
        for (int i = 1; i < N - 1; i++) { ds[i] = in<int>(), es[i] = in<int>(); }
        for (int i = 0; i < N; i++) { vss[es[i]].push_back(i); }
        for (int i = 0; i < M; i++) {
            const auto a = in<int>() - 1, b = in<int>() - 1, c = in<int>();
            if (es[a] == es[b]) {
                fg.add_edge(a, b, c, false);
                bg.add_edge(b, a, c, false);
            } else if (es[a] < es[b]) {
                fg.add_edge(a, b, c, false);
            } else {
                bg.add_edge(b, a, c, false);
            }
        }
        for (int h = 0; h <= 1000; h++) {
            const auto& vs = vss[h];
            for (int i = 0; i < vs.size(); i++) { mps[h][vs[i]] = i; }
        }

        using pii  = std::pair<int, int>;
        using ppi  = std::pair<pii, int>;
        using ippi = std::pair<int, ppi>;
        auto dsss  = make_v({N, N, 1 << 10}, inf_v<int>);
        min_heap<ippi> Q;
        dsss[0][0][1] = 0;
        Q.push({0, {{0, 0}, 1}});
        while (not Q.empty()) {
            const auto p = Q.top();
            Q.pop();
            const int d    = p.first;
            const int fp   = p.second.first.first;
            const int bp   = p.second.first.second;
            const int mask = p.second.second;
            if (dsss[fp][bp][mask] < d) { continue; }
            const int fe = es[fp], be = es[bp];
            const int Me = std::max(fe, be);
            for (const auto& e : fg[fp]) {
                const int nfp  = e.to();
                const int cost = e.cost();
                if (es[nfp] < Me) {
                    continue;
                } else if (es[nfp] == Me) {
                    const int nlind = mps[es[nfp]][nfp];
                    const int nmask = mask | (1 << nlind);
                    const int nd    = dsss[fp][bp][mask] + cost + (btest(mask, nlind) ? 0 : ds[nfp]);
                    if (dsss[nfp][bp][nmask] <= nd) { continue; }
                    dsss[nfp][bp][nmask] = nd, Q.push({nd, {{nfp, bp}, nmask}});
                } else {
                    const int nlind = mps[es[nfp]][nfp];
                    const int nmask = (1 << nlind);
                    const int nd    = dsss[fp][bp][mask] + cost + ds[nfp];
                    if (dsss[nfp][bp][nmask] <= nd) { continue; }
                    dsss[nfp][bp][nmask] = nd, Q.push({nd, {{nfp, bp}, nmask}});
                }
            }
            for (const auto& e : bg[bp]) {
                const int nbp  = e.to();
                const int cost = e.cost();
                if (es[nbp] < Me) {
                    continue;
                } else if (es[nbp] == Me) {
                    const int nlind = mps[es[nbp]][nbp];
                    const int nmask = mask | (1 << nlind);
                    const int nd    = dsss[fp][bp][mask] + cost + (btest(mask, nlind) ? 0 : ds[nbp]);
                    if (dsss[fp][nbp][nmask] <= nd) { continue; }
                    dsss[fp][nbp][nmask] = nd, Q.push({nd, {{fp, nbp}, nmask}});
                } else {
                    const int nlind = mps[es[nbp]][nbp];
                    const int nmask = (1 << nlind);
                    const int nd    = dsss[fp][bp][mask] + cost + ds[nbp];
                    if (dsss[fp][nbp][nmask] <= nd) { continue; }
                    dsss[fp][nbp][nmask] = nd, Q.push({nd, {{fp, nbp}, nmask}});
                }
            }
        }
        const int ans = dsss[N - 1][N - 1][1];
        outln(ans == inf_v<int> ? -1 : ans);
    }

    return 0;
}



Measured memory_bytes: 37716