#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

using int64 = long long;

const int MAX_N = 200000;
const int64 INF = (1LL << 50);

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;

    vector<int64> A(N);
    for (int i = 0; i < N; i++) {
        cin >> A[i];
    }
    vector<int64> dp(N, INF);
    for (int i = 0; i < N; i++) {
        if (A[i] - i <= 0) continue;
        *upper_bound(dp.begin(), dp.end(), A[i] - i) = A[i] - i;
    }

    int maxLength = lower_bound(dp.begin(), dp.end(), INF) - dp.begin();

    cout << N - maxLength << endl;

    return 0;
}