#include <bits/stdc++.h>

using namespace std;
ofstream g("pscnv.out");
class InParser {
private:
	FILE *fin;
	char *buff;
	int sp;

	char read_ch() {
		++sp;
		if (sp == 4096) {
			sp = 0;
			fread(buff, 1, 4096, fin);
		}
		return buff[sp];
	}

public:
	InParser(const char* nume) {
		fin = fopen(nume, "r");
		buff = new char[4096]();
		sp = 4095;
	}

	InParser& operator >> (int &n) {
		char c;
		while (!isdigit(c = read_ch()) && c != '-');
		int sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}

	InParser& operator >> (long long &n) {
		char c;
		n = 0;
		while (!isdigit(c = read_ch()) && c != '-');
		long long sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}
};
class OutParser {
private:
    FILE *fout;
    char *buff;
    int sp;

    void write_ch(char ch) {
        if (sp == 50000) {
            fwrite(buff, 1, 50000, fout);
            sp = 0;
            buff[sp++] = ch;
        } else {
            buff[sp++] = ch;
        }
    }


public:
    OutParser(const char* name) {
        fout = fopen(name, "w");
        buff = new char[50000]();
        sp = 0;
    }
    ~OutParser() {
        fwrite(buff, 1, sp, fout);
        fclose(fout);
    }

    OutParser& operator << (int vu32) {
        if (vu32 <= 9) {
            write_ch(vu32 + '0');
        } else {
            (*this) << (vu32 / 10);
            write_ch(vu32 % 10 + '0');
        }
        return *this;
    }

    OutParser& operator << (long long vu64) {
        if (vu64 <= 9) {
            write_ch(vu64 + '0');
        } else {
            (*this) << (vu64 / 10);
            write_ch(vu64 % 10 + '0');
        }
        return *this;
    }

    OutParser& operator << (char ch) {
        write_ch(ch);
        return *this;
    }
    OutParser& operator << (const char *ch) {
        while (*ch) {
            write_ch(*ch);
            ++ch;
        }
        return *this;
    }
};
vector <pair <int,int > > v[250005];
int n,m,a,b,x,y,c,ok,viz[250005],j;
void dfs (int x,int val)
{
    viz[x]=1;
    for (j=0;j<v[x].size();j++)
    {
        if (viz[v[x][j].first]==0&&val>=v[x][j].second)
        {
            dfs(v[x][j].first,val);
        }
    }
}
bool verif (int val)
{
    ok=0;
    for (int i=1;i<=n;i++)
    {
        viz[i]=0;
    }
    dfs(a,val);
    return viz[b];
}
int mij,i,st,dr,sol,maxim;
int main()
{
    InParser f("pscnv.in");
    OutParser g("pscnv.out");
    f>>n>>m>>a>>b;
    for (i=1;i<=m;i++)
    {
        f>>x>>y>>c;
        if (c>maxim)
        {
            maxim=c;
        }
        v[x].push_back({y,c});
    }
    st=1;
    dr=maxim;
    while (st<=dr)
    {
        mij=(st+dr)/2;
        if (verif(mij)==1)
        {
            sol=mij;
            dr=mij-1;
        }
        else
        {
            st=mij+1;
        }
    }
    g<<sol;
    return 0;
}