#include <bits/stdc++.h>

#define fr first
#define sc second
#define mk make_pair

using namespace std;

int n, ab[2000001], p[2000001], dp[200000], sz = 4;

struct st{
    int v, l, r, sum;
};

st t[1000001];

int get(int tl, int tr, int l, int r, int v) {
    if(l > r)
        return 0;
    if(tr == r && tl == l) {
        return t[v].sum;
    }else {
        int tm = (tr + tl) >> 1;
        return max(get(tl, tm, l, min(tm, r), t[v].l), get(tm + 1, tr, max(l, tm + 1), r, t[v].r));
    }
}

void goin(int tl, int tr, int x, int k, int v) {
    if(tr == tl)
        t[v].sum = max(k, t[v].sum);
    else {
        int tm = (tr + tl) >> 1;
        if(x <= tm) {
            if(t[v].l == 0)
                t[v].l = sz++;
            goin(tl, tm, x, k, t[v].l);
        }else {
            if(t[v].r == 0)
                t[v].r = sz++;
            goin(tm + 1, tr, x, k, t[v].r);
        }
        t[v].sum = max(t[t[v].l].sum, t[t[v].r].sum);
    }
}

int N = 1e9 + 1e5;

int main() {
    t[1].l = 2;
    t[1].r = 3;
    cin >> n;
    for(int i = 1; i <= n; i++)
        cin >> ab[i], ab[i] += n - i, dp[i] = 0;

    int ans = 0;
    for(int i = n; i >= 1; i--) {
        int k = get(1, N, ab[i], N, 1) + 1;
//      cout << k << endl;
        ans = max(ans, k);
        goin(1, N, ab[i], k, 1);
    }

    cout << n - ans << endl;
    return 0;
}