// G++ MACRO.CPP -STD=C++17
#include <bits/stdc++.h>
typedef long long ll;
const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;
using namespace std;
 
#define dump(x)  cout << #x << " = " << (x) << endl;
#define YES(n) cout << ((n) ? "YES" : "NO"  ) << endl
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define POSSIBLE(n) cout << ((n) ? "POSSIBLE" : "IMPOSSIBLE"  ) << endl
#define Possible(n) cout << ((n) ? "Possible" : "Impossible"  ) << endl
#define possible(n) cout << ((n) ? "possible" : "impossible"  ) << endl
 
#define SANKOU(n,a,b) cout << ((n) ? (#a) : (#b) ) << endl
 
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) for(int i=0;i<(n);++i)
#define REPR(i,n) for(int i=n;i>=0;i--)
 
#define FOREACH(x,a) for(auto& (x) : (a) )
 
#define WFA(d,v) REP(k,v)REP(i,v)REP(j,v)d[i][j]=min(d[i][j],d[i][k]+d[k][j])
 
#define SCOUT(x) cout<<(x)<<" "
#define ENDL cout<<endl
 
#define VECCIN(x) for(auto&youso_: (x) )cin>>youso_
#define VECIN2(x,y) REP(i,x.size())cin>>x[i]>>y[i]
#define VECCOUT(x) if(1){for(auto tt=x.begin();tt!=x.end();tt++){if(tt!=x.begin())cout<<" ";cout<<(*tt);}cout<<endl;}
 
#define ALL(obj) (obj).begin(),(obj).end()
 
#define EXIST(n,x) (find(ALL(n),x)!=n.end())
#define UNIQUE(obj) sort(ALL( obj )); obj.erase(unique(ALL(obj)),obj.end())
#define EN(x) if(1){cout<<#x<<endl;return 0;}
#define COUT(x) cout<<(x)<<endl
void CINT(){}
template <class Head,class... Tail>
void CINT(Head&& head,Tail&&... tail){
    cin>>head;
    CINT(move(tail)...);
}
#define CIN(...) int __VA_ARGS__;CINT(__VA_ARGS__)
#define LCIN(...) ll __VA_ARGS__;CINT(__VA_ARGS__)
#define SCIN(...) string __VA_ARGS__;CINT(__VA_ARGS__)
 
template <class T = ll>
T IN(){T x;cin>>x;return (x);}
 
template <class Head>
void VT(Head head){}
template <class Head,class Seco,class... Tail>
void VT(Head&& head,Seco&& seco,Tail&&... tail){
    seco.resize(head);
    VT(head,move(tail)...);
}
void VT2(){}
template <class Head,class... Tail>
void VT2(Head&& head,Tail&&... tail){
  VECCIN(head);
  VT2(move(tail)...);
}
 
template <class Head>
void VT3(Head&& head){}
template <class Head,class Seco,class... Tail>
void VT3(Head&& head,Seco&& seco,Tail&&... tail){
  seco[head]=IN();
  VT3(head,move(tail)...);
}
 
#define VC1(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);VT2(__VA_ARGS__); //aaabbbccc
#define VC2(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);REP(i,n)VT3(i,__VA_ARGS__); //abcabcabc
 
//#include <boost/multiprecision/cpp_int.hpp>
//using namespace boost::multiprecision; // cpp_int
 
#define P pair<ll,ll>
#define V vector<ll>
#define M map<ll,ll>
#define S set<ll>
 
#define pb(a) push_back(a)
#define mp make_pair

struct Edge {
  ll to, cost;  // 辺の接続先頂点, 辺の重み
  Edge(ll to, ll cost) : to(to), cost(cost) {}  // コンストラクタ
};

typedef vector<vector<Edge> > AdjList;  // 隣接リストの型
AdjList graph;  // グラフの辺を格納した構造体
                // graph[v][i]は頂点vから出るi番目の辺Edge

vector<ll> dist; // 最短距離

// 戻り値がtrueなら負の閉路を含む
bool bellman_ford(ll n, ll s) { // nは頂点数、sは開始頂点
  dist = vector<ll>(n, LINF);
  dist[s] = 0; // 開始点の距離は0
  for (ll i = 0; i < n*3; i++) {
    for (ll v = 0; v < n; v++) {
      for (ll k = 0; k < graph[v].size(); k++) {
        Edge e = graph[v][k];
        if (dist[v] != LINF && dist[e.to] > dist[v] + e.cost) {
          dist[e.to] = dist[v] + e.cost;
          if (i > n*2 && e.to == n-1){
            return true; // n回目にも更新があるなら負の閉路が存在
          }
        }
      }
    }
  }
  return false;
}



int main(){

  CIN(n,m);
  VC2(m,a,b,c);
  REP(i,m){a[i]--;b[i]--;}
  graph = AdjList(n);
  REP(i,m){
    graph[a[i]].push_back(Edge(b[i],-c[i]));
  }
  bool flag = bellman_ford(n,0);
  if(flag)EN(inf);
  COUT(-dist[n-1]);



  return 0;
}

Measured memory_bytes: 384