#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <vector>
using namespace std;
typedef long long LL;
const int N = 1e5 + 10;
int n, m;
LL w[N];
vector<int> e[N];
LL ans;
bool cmp(int a, int b)
{
    return a > b;
}
void dfs(int u)
{
    int k;
    cin >> w[u] >> k;
    for (int i = 1; i <= k; i++)
        e[u].push_back(n + 1), dfs(++n);
}
LL dfs2(int u)
{
    vector<LL> cur;
    for (int i = 0; i < e[u].size(); i++)
    {
        int j = e[u][i];
        LL t = dfs2(j);
        ans += t / m;
        t %= m;
        if (t)
            cur.push_back(t);
    }
    sort(cur.begin(), cur.end());
    LL sum = 0;
    for (int i = 0; i < cur.size(); i++)
    {
        sum += cur[i];
        if (sum > m)
        {
            sum -= cur[i];
            ans += cur.size() - i;
            break;
        }
    }
    return w[u] + sum;
}
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> m;
    dfs(++n);
    LL t = dfs2(1);
    ans += (t - 1) / m + 1;
    cout << ans << endl;
    return 0;
}