为什么第一个点会WA……

#include <bits/stdc++.h>
using namespace std;

const int N = 110, M = 110;

bool cant[M][N][N], closed[M][N], vis[M];
struct edge_t
{
    int to, nxt, val;
} edge[2 * N * N];
int head[N], tot = 0;
long long dist[M][M][N], cost[M][M];
long long dp[M];
int n, m, k, e, d;

void add(int u, int v, int w)
{
    edge[tot] = {v, head[u], w}, head[u] = tot++;
    edge[tot] = {u, head[v], w}, head[v] = tot++;
}
void spfa(int a, int b)
{
    memset(vis, false, sizeof(vis));
    dist[a][b][1] = 0;
    queue<int> q;
    q.push(1);
    vis[1] = true;
    while (!q.empty())
    {
        int p = q.front();
        q.pop();
        vis[p] = false;
        for (int ed = head[p]; ed != -1; ed = edge[ed].nxt)
        {
            int to = edge[ed].to, val = edge[ed].val;
            if (cant[to][a][b])
                continue;
            if (dist[a][b][to] > dist[a][b][p] + val)
            {
                dist[a][b][to] = dist[a][b][p] + val;
                if (!vis[to])
                    q.push(to), vis[to] = true;
            }
        }
    }
}

int main()
{
    memset(head, -1, sizeof(head));
    for (int i = 0; i < N; i++)
        for (int j = 0; j < N; j++)
            for (int k = 0; k < N; k++)
                dist[i][j][k] = 1e8;
    scanf("%d%d%d%d", &n, &m, &k, &e);
    for (int i = 0; i < e; i++)
    {
        int u, v, w;
        scanf("%d%d%d", &u, &v, &w);
        add(u, v, w);
    }
    scanf("%d", &d);
    for (int i = 0; i < d; i++)
    {
        int p, a, b;
        scanf("%d%d%d", &p, &a, &b);
        for (int j = a; j <= b; j++)
            closed[p][j] = true;
    }
    bool flag;
    for (int p = 1; p <= n; p++)
        for (int i = 1; i <= n; i++)
        {
            flag = false;
            for (int j = i; j <= n; j++)
            {
                if (closed[p][j])
                    flag = true;
                if (flag)
                    cant[p][i][j] = true;
            }
        }
    for (int i = 1; i <= n; i++)
        for (int j = i; j <= n; j++)
            spfa(i, j), cost[i][j] = dist[i][j][m];
    memset(dp, 0x7f, sizeof(dp));
    for (int i = 1; i <= n; i++)
    {
        dp[i] = cost[1][i] * i;
        for (int j = i - 1; j >= 0; j--)
            dp[i] = min(dp[i], dp[j] + cost[j + 1][i] * (i - j) + k);
    }
    printf("%d", dp[n]);
    return 0;
}