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

int N;

int main() {
    cin >> N;
    vector<bool> keys(N, false);
    vector<int> rooms;
    int a;
    for (int i = 0; i <= N; i++)
    {
        cin >> a;
        rooms.push_back(a);        
    }
    int loc = 0;
    int offset = 0;
    while (loc != N)
    {
        loc = 0;
        for (int i = 0; i < N; i++)
        {
            loc++;
            keys[(rooms[i] + offset) % N] = true;
            if (keys[i]) continue;
            offset++;
            break;
        }
    }
    cout << offset;
}