#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <random>

using namespace __gnu_pbds;
using namespace std;
template<class T> using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3,unroll-loops")

mt19937 rnd(238);

#define len(a) (int) a.size()
#define pb push_back
#define pbb pop_back
#define all(a) a.begin(), a.end()
#define rev reverse
#define ff first
#define ss second
#define vec vector
#define str string
#define ll long long
#define lb lower_bound
#define ub upper_bound
#define umap unordered_map
#define pri pair<int, int>
#define prl pair<ll, ll>

const int MOD = 1e9 + 7;
const int BLOCK_SZ = 1000;
const ll inf = 1e18;
const int INF = 1e9;
const int mod = 1e9 + 7;
const int sz = 4000;
struct robot {
    ll x, p, d;
};

void solve() {
    int n;
    cin >> n;
    vector<robot> a(n);
    for (int i = 0; i < n; i++) cin >> a[i].x >> a[i].p >> a[i].d;
    ll ans = inf;
    for (int i = -1; i < n; i++) {
        bool ok = true;
        for (int j = 0; j + 1 <= i; j++) {
            if (a[j + 1].x - a[j].x > a[j].p) ok = false;
        }
        for (int j = n - 1; j - 1 > i; j--) {
            if (a[j].x - a[j - 1].x > a[j].p) ok = false;
        }
        if (ok) {
            if (a[i].x + a[i].p >= a[i + 1].x - a[i + 1].p) {
                ll cnt = 0;
                for (int j = 0; j < n; j++) {
                    if (j <= i && a[j].d == -1) cnt++;
                    if (j > i && a[j].d == 1) cnt++;
                }
                ans = min(ans, cnt);
            }
        }
    }
    if (ans == inf) cout << -1;
    else cout << ans;
}


signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int _ = 1;
    while (_--) solve();
}