#include <iostream>
#include <stdio.h>
#include <vector>
using namespace std;
typedef long long llong;

int n,m;
vector< pair<int,int> > Graph[1011];

llong dist[1011];

bool BellmanFord()
{
    int i,j,in;
    bool upd;

    for (i=1;i<=n+1;i++)
    {
        upd = false;

        for (j=1;j<=n;j++)
        {
            for (in=0;in<Graph[j].size();in++)
            {
                if (dist[j] + (llong)Graph[j][in].second < dist[ Graph[j][in].first ])
                {
                    dist[ Graph[j][in].first ] = dist[j] + (llong)Graph[j][in].second;
                    upd = true;
                }
            }
        }

        if (!upd)
            break;
    }

    return (i <= n);
}

bool Okay(int L)
{
    int i,j;
    bool ans;

    for (i=1;i<=n;i++)
    {
        for (j=0;j<Graph[i].size();j++)
        {
            Graph[i][j].second = L - Graph[i][j].second;
        }
    }

    ans = BellmanFord();

    for (i=1;i<=n;i++)
    {
        for (j=0;j<Graph[i].size();j++)
        {
            Graph[i][j].second = L - Graph[i][j].second;
        }
    }

    return ans;
}

int main()
{
    freopen("graph.in","r",stdin);
    freopen("graph.out","w",stdout);

    int i,j;
    int a,b,c;
    int l,r,mid,best;

    scanf("%d %d",&n,&m);

    for (i=1;i<=m;i++)
    {
        scanf("%d %d %d",&a,&b,&c);

        Graph[a].push_back(make_pair(b,c));
    }

    l = -1000000001;
    r = 1000000001;

    while(l<=r)
    {
        mid = (l+r)/2;

        if (Okay(mid))
        {
            best = mid;
            r = mid - 1;
        }
        else
        {
            l = mid + 1;
        }
    }

    if (best == -1000000001)
    {
        printf("-inf\n");
    }
    else
    {
        printf("%d\n",best);
    }

    return 0;
}