public Main() {
try {
BufferedReader in;
in = new BufferedReader(new InputStreamReader(System.in)); // Used for CCC
int numLights = Integer.parseInt(in.readLine());
int[] states = new int[numLights];
for (int i = 0; i < numLights; i++) {
states[i] = Integer.parseInt(in.readLine());
}
ArrayDeque<Scenario> Q = new ArrayDeque<Scenario>();
HashMap<String, Integer> dp = new HashMap<String, Integer>();
int moves = 0;
Q.addLast(new Scenario(states));
while (!Q.isEmpty()) {
int size = Q.size();
for (int q = 0; q < size; q++) {
Scenario temp = Q.removeFirst();
if (isEmpty(temp.states)) {
System.out.println(moves);
return;
} else {
for (int i = 0; i < temp.states.length; i++) {
if (temp.states[i] == 0) {
int[] newArr = Arrays.copyOf(temp.states, temp.states.length);
newArr[i] = 1;
newArr = fixArray(newArr);
String arr = "";
for (int p = 0; p < newArr.length; p++) arr += newArr[p];
if (dp.get(arr) == null) {
dp.put(arr, moves);
Q.addLast(new Scenario(newArr));
} else {
int val = dp.get(arr);
if (val != 0 && moves < val) {
dp.put(arr, moves);
Q.addLast(new Scenario(newArr));
}
}
// outputArr(newArr);
}
}
}
}
moves++;
}
} catch (IOException e) {
System.out.println("IO: General");
}
}
static void solve() {
int r = in.nextInt();
int c = in.nextInt();
int sy = in.nextInt() - 1;
int sx = in.nextInt() - 1;
int gy = in.nextInt() - 1;
int gx = in.nextInt() - 1;
char[][] t = new char[r][c];
for (int i = 0; i < r; i++) {
t[i] = in.next().toCharArray();
}
ArrayDeque<int[]> que = new ArrayDeque<>();
BitSet visited = new BitSet();
que.add(new int[] {sy, sx, 0});
visited.set(sy * c + sx);
int[] dx = {0, 1, 0, -1};
int[] dy = {1, 0, -1, 0};
int[][] dist = new int[r][c];
while (!que.isEmpty()) {
int[] p = que.pollFirst();
int cy = p[0];
int cx = p[1];
int d = p[2];
dist[cy][cx] = d;
for (int i = 0; i < 4; i++) {
int ny = cy + dy[i];
int nx = cx + dx[i];
if (ny < 0 || nx < 0 || r <= ny || c <= nx) continue;
if (visited.get(ny * c + nx) || t[ny][nx] == '#') continue;
que.add(new int[] {ny, nx, d + 1});
visited.set(ny * c + nx);
}
}
out.println(dist[gy][gx]);
}