#include <fstream>
#include <cstdlib>
#include <cstdio>
using namespace std;
ifstream in("longest.in");
ofstream out("longest.out");
int n,m;
long long pic[1501][1501]={0};
long long ans=-1;
int dfs(int num,int len)
{
	if(num==n)
	{
		if(len>=ans)
			ans=len;
	}else
	{
		for(int i=num+1;i<=n;i++)
		{
			if(pic[num][i]!=0)
				dfs(i,len+pic[num][i]);
		}
	}
}

int main()
{
	in>>n>>m;
	for(int i=0;i<m;i++)
	{
		int a,b,c;
		in>>a>>b>>c;
		pic[a][b]=c;
	}
	dfs(1,0);
	out<<ans<<endl;
	return 0;
}