#include <assert.h>
#include <stdio.h>
#include <string.h>
#define N 200000
#define N_ (1 << 18) /* N_ = pow2(ceil(log2(N))) */
int min(int a, int b) { return a < b ? a : b; }
int max(int a, int b) { return a > b ? a : b; }
int sum[N_ * 2], pref[N_ * 2], suf[N_ * 2], n1, n_;
void pul(int i) {
int l = i << 1, r = l | 1;
sum[i] = sum[l] + sum[r];
pref[i] = min(pref[l], sum[l] + pref[r]);
suf[i] = max(suf[l] + sum[r], suf[r]);
}
void build(int n) {
int i;
n1 = n;
n_ = 1;
while (n_ < n)
n_ <<= 1;
for (i = 0; i < n_; i++)
if (i < n)
sum[n_ + i] = pref[n_ + i] = suf[n_ + i] = -1;
for (i = n_ - 1; i > 0; i--)
pul(i);
}
int kk[N];
void update(int i, int x) {
i += n_;
pref[i] = suf[i] = sum[i] += x;
while (i > 1)
pul(i >>= 1);
}
int query(int i) {
int l, r, x, y;
x = y = 0;
for (l = n_ + 0, r = n_ + i - 1; l <= r; l >>= 1, r >>= 1)
if ((r & 1) == 0)
x = max(x, suf[r] + y), y += sum[r], r--;
x = max(x, suf[1] + y);
for (l = n_ + i, r = n_ + n_ - 1; l <= r; l >>= 1, r >>= 1)
if ((l & 1) == 1) {
if (x + pref[l] <= 0) {
i = l;
while (i < n_)
if (x + pref[i << 1 | 0] <= 0)
i = i << 1 | 0;
else
x += sum[i << 1 | 0], i = i << 1 | 1;
return i - n_;
} else
x += sum[l];
l++;
}
if (x + pref[1] > 0)
return -1;
i = 1;
while (i < n_)
if (x + pref[i << 1 | 0] <= 0)
i = i << 1 | 0;
else
x += sum[i << 1 | 0], i = i << 1 | 1;
return i - n_;
}
int add(int i) {
update(i, 1), kk[i]++;
return query(i);
}
int delete(int i) {
int j = query(i);
update(i, -1), kk[i]--;
return j;
}
char used[N];
int solve_winners(int *kk, int n) {
int i, j, k, sum;
memset(used, 0, n * sizeof *used);
k = 0, sum = 0;
for (i = 0; i < n; i++)
if (kk[i] > 0) {
k = kk[i] - 1;
if (i == 0 && k > 0)
used[i] = 1, k--, sum ^= i;
break;
}
for (j = i + 1; j <= i + n; j++) {
if (j != i + n)
k += kk[j % n];
if (!used[j % n] && k > 0)
used[j % n] = 1, k--, sum ^= j % n;
}
for (j = i + 1; j <= i + n; j++)
if (!used[j % n] && k > 0)
used[j % n] = 1, k--, sum ^= j % n;
return sum;
}
int main() {
static int aa[N * 2];
int n, r, p, p_, i, i_, a_, mn;
scanf("%d%d", &n, &r);
for (i = 0; i < n * 2; i++)
scanf("%d", &aa[i]), aa[i]--;
build(n);
a_ = aa[0];
if (a_ == 0)
i_ = n - 1;
else if (a_ > n) {
add(n - 1 - 0);
for (i = 0; i < n * 2; i++)
if (aa[i] > a_)
add(n - 1 - (i / 2));
p_ = n, i_ = -1;
for (i = 0; i < n; i++) {
if (i > 0) {
if (aa[i * 2] > a_)
delete(n - 1 - i), add(n - 1 - (i - 1));
aa[(i - 1) * 2] = aa[i * 2], aa[i * 2] = a_;
}
p = n - 1 - add(n - 1 - i), delete(n - 1 - i);
if (p_ >= p)
p_ = p, i_ = i;
}
} else {
for (i = 0; i < n * 2; i++)
if (aa[i] < a_)
add(i / 2);
mn = 0;
while (kk[mn] == 0)
mn++;
p_ = n, i_ = -1;
for (i = 0; i < n; i++) {
int p1;
if (i > 0) {
if (aa[i * 2] < a_) {
delete(i), add(i - 1);
if (mn == i)
mn--;
}
aa[(i - 1) * 2] = aa[i * 2], aa[i * 2] = a_;
}
p1 = solve_winners(kk, n), add(i), p1 ^= solve_winners(kk, n), delete(i);
if (i < mn) {
if (kk[mn] == 1 || mn == 0)
delete(mn), p = add(mn);
else
delete(mn), delete(mn), add((mn + 1) % n), p = delete((mn + 1) % n), p ^= add(mn), p ^= add(mn);
} else if (i > mn) {
int push;
delete(mn), push = kk[mn] == 2 && mn != 0;
if (push)
delete(mn), add((mn + 1) % n);
p = add(i), delete(i);
if (push)
delete((mn + 1) % n), add(mn);
add(mn);
} else {
if (i == 0)
p = 0;
else
delete(mn), p = add((i + 1) % n), delete((i + 1) % n), add(mn);
}
p = (p - r % n + n) % n;
p1 = (p1 - r % n + n) % n;
if (i > mn)
assert(p == p1);
if (p_ >= p1)
p_ = p1, i_ = i;
}
}
printf("%d\n", i_ + 1);
return 0;
}
