#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define svec(v) cout<<#v<<":";rep(kbrni,v.size())cout<<" "<<v[kbrni];cout<<endl
#define sset(s) cout<<#s<<":";each(kbrni,s)cout<<" "<<kbrni;cout<<endl
#define smap(m) cout<<#m<<":";each(kbrni,m)cout<<" {"<<kbrni.first<<":"<<kbrni.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 51;

struct data
{
    int go,back,st;
    bool operator< (const data& ano) const {
        if(go == ano.go){
            if(back == ano.back){
                return st < ano.st;
            }else{
                return back < ano.back;
            }
        }else{
            return go < ano.go;
        }
    }
    void print(){
        cout << go << " " << back << " " << st << "\n";
    }
};

struct edge
{
    int to,cost;
};

vector<edge> g1[MAX_N],g2[MAX_N];
int num[MAX_N];
int dist[MAX_N][MAX_N][(1 << 10)];

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    while(1){
        map<int,int> hset;
        int n,m;
        cin >> n >> m;
        if(n == 0 && m == 0){
            break;
        }
        rep(i,n){
            rep(j,n){
                rep(k,(1 << 10)){
                    dist[i][j][k] = INF;
                }
            }
        }
        rep(i,n){
            g1[i].clear(),g2[i].clear();
        }
        vi c(n,0),h(n,0);
        rep(i,n-2){
            cin >> c[i+1] >> h[i+1];
        }
        h[n-1] = 1000;
        rep(i,n){
            num[i] = hset[h[i]];
            hset[h[i]]++;
        }
        rep(i,m){
            int x,y,z;
            cin >> x >> y >> z;
            --x,--y;
            if(h[x] < h[y]){
                g1[x].pb((edge){y,z});
            }else if(h[x] > h[y]){
                g2[y].pb((edge){x,z});
            }else{
                g1[x].pb((edge){y,z});
                g2[y].pb((edge){x,z});
            }
        }
        queue<data> que;
        que.push((data){0,0,1});
        dist[0][0][1] = 0;
        while(!que.empty()){
            data p = que.front();
            que.pop();
            // p.print();
            // show(dist[p]);
            if(h[p.go] <= h[p.back]){
                for(auto& e : g1[p.go]){
                    int v = e.to;
                    int cs = e.cost;
                    data nx = p;
                    nx.go = v;
                    if(h[v] >= h[p.back]){
                        if(h[v] == h[p.back]){
                            bool ok = (nx.st & (1 << num[v]));
                            nx.st |= (1 << num[v]);
                            int nxc = dist[p.go][p.back][p.st]+cs+(ok?0:c[v]);
                            if(dist[nx.go][nx.back][nx.st] > nxc){
                                dist[nx.go][nx.back][nx.st] = nxc;
                                que.push(nx);
                            }
                        }else{
                            nx.st = (1 << num[v]);
                            int nxc = dist[p.go][p.back][p.st]+cs+c[v];
                            if(dist[nx.go][nx.back][nx.st] > nxc){
                                dist[nx.go][nx.back][nx.st] = nxc;
                                que.push(nx);
                            }
                        }
                    }else{
                        int nxc = dist[p.go][p.back][p.st]+cs+c[v];
                        if(dist[nx.go][nx.back][nx.st] > nxc){
                            dist[nx.go][nx.back][nx.st] = nxc;
                            que.push(nx);
                        }
                    }
                }
            }
            if(h[p.go] >= h[p.back]){
                for(auto& e : g2[p.back]){
                    int v = e.to;
                    int cs = e.cost;
                    data nx = p;
                    nx.back = v;
                    if(h[v] >= h[p.go]){
                        if(h[v] == h[p.go]){
                            bool ok = (nx.st & (1 << num[v]));
                            nx.st |= (1 << num[v]);
                            int nxc = dist[p.go][p.back][p.st]+cs+(ok?0:c[v]);
                            if(dist[nx.go][nx.back][nx.st] > nxc){
                                dist[nx.go][nx.back][nx.st] = nxc;
                                que.push(nx);
                            }
                        }else{
                            nx.st = (1 << num[v]);
                            int nxc = dist[p.go][p.back][p.st]+cs+c[v];
                            if(dist[nx.go][nx.back][nx.st] > nxc){
                                dist[nx.go][nx.back][nx.st] = nxc;
                                que.push(nx);
                            }
                        }
                    }else{
                        int nxc = dist[p.go][p.back][p.st]+cs+c[v];
                        if(dist[nx.go][nx.back][nx.st] > nxc){
                            dist[nx.go][nx.back][nx.st] = nxc;
                            que.push(nx);
                        }
                    }
                }
            }
        }
        if(dist[n-1][n-1][1] == INF){
            cout << "-1\n";
        }else{
            cout << dist[n-1][n-1][1] << "\n";
        }
    }
    return 0;
}



Measured memory_bytes: 14112