#include <fstream>
#include <vector>
#include <cstring>
#define nmax 250005
using namespace std;
class instream {
    public:
        instream() {}
        instream(const char *file_name) {
            input_file=fopen(file_name,"r");
            cursor=0;
            fread(buffer,SIZE,1,input_file);
        }
        inline instream &operator >>(int &n) {
            while((buffer[cursor]<'0'||buffer[cursor]>'9')&&buffer[cursor]!='-') {
                advance();
            }
            int semn=1;
            if (buffer[cursor]=='-')
                semn=-1,advance();
            n=0;
            while('0'<=buffer[cursor]&&buffer[cursor]<='9') {
                n=n*10+buffer[cursor]-'0';
                advance();
            }
            n*=semn;
            return *this;
        }
    private:
        FILE *input_file;
        static const int SIZE=1<<15;
        int cursor;
        char buffer[SIZE];
        inline void advance() {
            ++ cursor;
            if(cursor==SIZE) {
                cursor=0;
                fread(buffer,SIZE,1,input_file);
            }
        }
};
instream f("pscnv.in");
ofstream g("pscnv.out");
vector <pair<int,int> > v[nmax];
int n,m,k,x,y,d[nmax];

void dfs(int x)
{
    int i,z,t;
    d[x]=1;
    if (d[y])
        return;
    for (i=0;i<v[x].size();i++) {
        z=v[x][i].first;
        t=v[x][i].second;
        if (t<=k&&d[z]==0)
            dfs(z);
    }
}
int possible(int p)
{
    if (p<1)
        return 0;
    memset(d,0,sizeof(d));
    k=p;
    dfs(x);
    return d[y];
}
int main()
{
    int i,j,l,p;
    f>>n>>m>>x>>y;
    if (x==y) {
        g<<1<<'\n';
        return 0;
    }
    for (i=1;i<=m;i++) {
        f>>j>>l>>p;
        v[j].push_back(make_pair(l,p));
    }
    for (i=0,j=1<<9;j;j>>=1)
        if (possible(1000-(i+j)))
            i+=j;
    g<<1000-i<<'\n';
    return 0;
}