#include<bits/stdc++.h>
#define pb emplace_back
#define pi pair<int,int>
#define fi first
#define se second
#define mp make_pair
using namespace std;
using ll = long long;
using db = double;

constexpr int MAXSIZE = 1 << 20;
char buf[MAXSIZE], *p1, *p2;
#define gc() getchar()//(p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, MAXSIZE, stdin), p1 == p2) ? EOF : *p1++)

int rd() {int x = 0, f = 1;char c = gc();while (!isdigit(c)) {if (c == '-') f = -1;c = gc();}while (isdigit(c)) x = x * 10 + (c ^ 48), c = gc();return x * f;}

const int N = 2e5 + 7;
int i, j, k, n, m, a[N];
int l[N], r[N], f[N], v[N], vis[N];
pi c[N];
priority_queue<pi> q;
vector<int> d[N];

int fl(int x) {return x == l[x] ? x : l[x] = fl(l[x]);}
int fr(int x) {return x == r[x] ? x : r[x] = fr(r[x]);}

int dis(int x, int y) {return y - x + (x > y) * n;}

int val(int u, int x) {return dis(v[u], x) + f[x] + 1;}

void add(int x) {
	int L = fl((x-1+n)%n), R = fr((x+1)%n);
	for(int u : d[L]) if(val(u, x) < f[u]) q.push({-(f[u] = val(u, x)), u});
	if(L != R) for(int u : d[R]) if(val(u, x) < f[u]) q.push({-(f[u] = val(u, x)), u});
}

signed main() {
//	freopen(".in", "r", stdin);
//	freopen(".out", "w", stdout);
//	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	n = rd(), k = rd();
	for(i = 0; i < n; i++) a[i] = rd();
	for(i = 0; i < n; i++) c[i] = {v[i] = (i + a[i]) % n, i};
	sort(c, c + n);
	for(i = 0; i < n; i++) d[i].pb(c[i].se);
	for(i = 0; i < n; i++) l[i] = d[i].size() ? i : (i-1+n)%n;
	for(i = 0; i < n; i++) r[i] = d[i].size() ? i : (i+1)%n;
	memset(f, 0x3f, sizeof f);
	f[k] = 0, add(k);
	while(q.size()) {
		pi t = q.top(); q.pop();
		int x = t.se;
		if(vis[x]) continue;
		vis[x] = 1;
		if(!x) return printf("%d\n", f[0]),0;
		add(x);
	}
	printf("%d\n", f[0]);
	return 0;
}