#include <stdio.h>
#include <vector>
#include <list>
#include <queue>
#include <algorithm>
#define NMax 250010
#define INF 0x3f3f3f3f
using namespace std;

const char IN[]="pscnv.in",OUT[]="pscnv.out";
int N,M,X,Y;
int T[NMax];
bool InQue[NMax];
vector<pair<int,int> > ad[NMax];
vector<int> v[1010];

void Dijkstra()
{
	int i,x,l;
	for (i=0;i<=N;++i) T[i]=INF;
	T[X]=0;
	l=0;v[0].push_back(X);
	for (i=0;i<N;++i)
	{
		for (x=0;x==0;)
		{
			for (;l<=1001 && v[l].empty();++l);
			if (l>1001) break;
			
			if (T[v[l].back()]!=l){
				v[l].pop_back();
				continue;
			}
			
			x=v[l].back();
			v[l].pop_back();
			
			if (InQue[x]) x=0;
		}
		
		if (x==0) break;
		InQue[x]=true;
		
		for (typeof(ad[x].begin()) it=ad[x].begin();it<ad[x].end();++it)
			if ( max(T[x],it->second)<T[it->first])
				T[it->first]=max(T[x],it->second),
				v[max(T[x],it->second)].push_back(it->first);
	}
}

inline void read(int &x,int &y,int &z)
{
	static char s[256],*r;
	static int a[3],i;
	
	gets(s);r=s;
	
	for (i=0;i<3;++i)
	{
		a[i]=0;
		while (*r && (*r<'0' || *r>'9')) ++r;
		while (*r>='0' && *r<='9') 
			a[i]= a[i]*10+*r-'0',
			++r;
	}
	x=a[0];y=a[1];z=a[2];
}

int main()
{
	int i,x,y,c;
	freopen(IN,"r",stdin);
	scanf("%d%d%d%d\n",&N,&M,&X,&Y);
	for (i=0;i<M;++i)
		//scanf("%d%d%d",&x,&y,&c),
		read(x,y,c),
		ad[x].push_back(make_pair(y,c)),
		ad[y].push_back(make_pair(x,c));
	fclose(stdin);
	
	Dijkstra();
	
	freopen(OUT,"w",stdout);
	printf("%d\n",T[Y]);
	fclose(stdout);
	return 0;
}