#include <iostream>
#include<cstdio>
using namespace std;
FILE *f=fopen("ubuntzei.in","r");
FILE *g=fopen("ubuntzei.out","w");
int v[2001],n,m,k,i,a,b,l;
int main()
{


    fscanf(f,"%d%d%d",&n ,&m, &k);
    for(i=1;i<=n;i++)
            v[i]=-1;

    for(i=1;i<=m;i++)
        {fscanf(f,"%d%d%d",&a,&b,&l);
         if(v[b]<0&&v[a]<0)
            v[b]=l;
         else
         if(v[b]<0&&v[a]>0)
            v[b]=v[a]+l;
        else
         if(v[a]+l<v[b])
                v[b]=v[a]+l;
        }
    fprintf(g,"%d", v[n]);
    return 0;
}