/*
[templates]: 
duipai
spjdp
compre
addhis
floor_sum
treedfs
matrix
network_flow
polynomial
lca
bitset
valuesgt
fenwick
erbitree
*/
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx")
#include<bits/stdc++.h>
using namespace std;
#define int long long
//use ll instead of int.
#define f(i, a, b) for(int i = (a); i <= (b); i++)
#define cl(i, n) i.clear(),i.resize(n);
#define endl '\n'
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int inf = 1e18;
//#define cerr if(false)cerr
//#define freopen if(false)freopen
mt19937 rng(time(0)); 
int rnd(int l, int r) {return rng() % (r-l+1) + l; }
#define watch(x) cerr  << (#x) << ' '<<'i'<<'s'<<' ' << x << endl
void pofe(int number, int bitnum) {
    string s; f(i, 0, bitnum) {s += char(number & 1) + '0'; number >>= 1; } 
    reverse(s.begin(), s.end()); cerr << s << endl; 
    return;
}
template <typename TYP> void cmax(TYP &x, TYP y) {if(x < y) x = y;}
template <typename TYP> void cmin(TYP &x, TYP y) {if(x > y) x = y;}
//调不出来给我对拍！
//use std::array.
vector<pii> g[300200]; int n, m; int dis[300030]; 
bool ok(int mid) {
    queue<int> q; q.push(1); 
    f(i, 1, n) dis[i] = inf; 
    dis[1] = 0; 
    while(!q.empty()) {
        int now = q.front(); q.pop(); 
        if(now == n) return 1; 
        for(pii i : g[now]) {
            if(dis[i.first] != inf) continue; 
            if(i.second * (dis[now] + 1) > mid) continue; 
            dis[i.first] = dis[now] + 1; 
            q.push(i.first); 
        }
    }
    return 0; 
}
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    //freopen();
    //freopen();
    //time_t start = clock();
    //think twice,code once.
    //think once,debug forever.
    cin >> n >> m; 
    f(i, 1, m) {
        int a, b, c; cin >> a >> b >> c; 
        g[a].push_back({b, c}); 
    }
    int lo = 0, hi = 3e14; 
    while(lo < hi) {
        int mid = (lo + hi) >> 1; 
        if(ok(mid)) hi = mid;
        else lo = mid + 1; 
    }
    cout << lo << endl; 
    //time_t finish = clock();
    //cout << "time used:" << (finish-start) * 1.0 / CLOCKS_PER_SEC <<"s"<< endl;
    return 0;
}