#include <bits/stdc++.h>
using namespace std;
const int N = 1010, inf = 1e9;
typedef pair<int, int> pll;
typedef long long ll;
int n, m, x;
int d[N][N];
void floyd()
{

    for (int k = 1; k <= n; k++)
    {
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
            }
        }
    }
}
void solve()
{
    cin >> n>>m>>x;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            if (i != j)
            {
                d[i][j] = inf;
            }
            else
                d[i][j] = 0;
        }
    }
    while (m--)
    {
        int a, b, c;
        cin >> a >> b >> c;

        d[a][b] = c;
    }

    floyd();

    int res = -1e9;
    for (int i = 1; i <= n; i++)
    {
        if(i!=x)res = max(res, d[i][x]+d[x][i]);
        //cout<<d[i][x]<<endl;

    }
    cout <<  res << endl;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t = 1;
    // cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}