#include<bits/stdc++.h>
using namespace std;
inline int read() {
    int x=0, w=1;
    char ch=0;
    while (ch<'0' || ch>'9') {
        if (ch=='-')
            w=-1;
        ch=getchar();
    }
    while (ch>='0' && ch<='9') 
        x=(x<<3)+(x<<1)+ch-'0', ch=getchar();
    return x*w;
}
inline void write(long long x) {
    if (x<0) 
        putchar('-'), x=-x;
    if (x>9) 
        write(x/10);
    putchar(x%10+'0');
}
int N,S,head[500004],cnt=0,vis[500004];
long long dp[500004],f[500004];
struct node{
    int to,next,w;
}e[1000004];
void add(int u,int v,int w){
    e[++cnt].to=v;e[cnt].next=head[u];e[cnt].w=w;head[u]=cnt;
}
void treedp(int root){
    vis[root]=1;long long maxx=0,p=0;int num=0;
    for(int i=head[root];i;i=e[i].next){
        int v=e[i].to,w=e[i].w;
        if(vis[v]) continue;
        treedp(v);num++;
        maxx=max(maxx,(long long)f[v]+w);
        p=(long long) p+f[v]+w;
        dp[root]+=dp[v];
    }
    dp[root]=(long long)maxx*num+dp[root]-p;
    f[root]=maxx;
}
int main(){
    N=read(),S=read();
    for(int i=1;i<N;i++){
        int x=read(),y=read(),z=read();
        add(x,y,z);add(y,x,z);
    }
    treedp(S);
    write(dp[S]);
}

#include<bits/stdc++.h>
using namespace std;
const int N = 500000 + 5;
int n, s, head[N], cnt, maxn[N];
long long ans;
struct node{
    int u, v, nxt, w;
}edge[N << 1];
void add(int u, int v, int val){
    edge[++ cnt].u = u;
    edge[cnt].v = v;
    edge[cnt].w = val;
    edge[cnt].nxt = head[u];
    head[u] = cnt;
}
void dfs(int now, int fa){
    for(int i = head[now]; i; i = edge[i].nxt){
        int to = edge[i].v;
        if(to == fa) continue;
        dfs(to, now);
    }
    for(int i = head[now]; i; i = edge[i].nxt){
        int to = edge[i].v;
        if(to == fa) continue;
        maxn[now] = max(maxn[now], edge[i].w);
    }
    for(int i = head[now]; i; i = edge[i].nxt){
        int to = edge[i].v;
        if(to == fa) continue;
        ans += (maxn[now] - edge[i].w);
    }
    for(int i = head[fa]; i; i = edge[i].nxt){
        int to = edge[i].v;
        if(to == now) edge[i].w += maxn[now];
    }
}
int main(){
    scanf("%d %d", &n, &s);
    for(int i = 1, x, y, z; i < n; i ++){
        scanf("%d %d %d", &x, &y, &z);
        add(x, y, z); add(y, x, z);
    }
    dfs(s, 0);
    printf("%lld\n", ans);
    return 0;
}