#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int>P(N);
    vector<long long>sum(N+1);
    for(int i = 0; i < N; i++) {
        cin >> P[i];
        P[i]--;
        sum[P[i]] = i+1;
    }
    long long ans = 0;
    for(int i = 1; i < N; i++) {
        ans = max(ans,sum[i-1]-sum[i]);
        sum[i] += sum[i-1];
    }
    cout << ans << endl;
}