参考答案：

#include<iostream>
#include<cstring>

using namespace std;

const int N = 30010;
int n, m, k;
int dis[N], last[N];

struct Edge
{
    int a, b, c;
}edge[N];

int bellman_ford()
{
    memset(dis, 0x3f, sizeof(dis));
    dis[1] = 0;

    for (int i = 1; i <= k; ++i)
    {
        memcpy(last, dis, sizeof(dis));
        for (int j = 1; j <= m; ++j)
        {
            auto t = edge[j];
            dis[t.b] = min(dis[t.b], last[t.a] + t.c);
        }
    }

    return dis[n];
}
int main()
{
    cin >> n >> m >> k;

    for (int i = 1; i <= m; ++i)
    {
        cin >> edge[i].a >> edge[i].b >> edge[i].c;
    }

    if (bellman_ford() > 0x3f3f3f3f / 2) cout << "No path";
    else cout << dis[n];

    return 0;
}