#include <stdio.h>
#include <string.h>
#define N 200000
char used[N];
int solve_losers(int *kk, int n) {
int i, k, sum;
memset(used, 0, n * sizeof *used);
k = 0, sum = 0;
for (i = n - 1; i >= 0; i--) {
k += kk[i];
if (!used[i] && k > 0)
used[i] = 1, k--, sum ^= i;
}
for (i = n - 1; i >= 0; i--)
if (!used[i] && k > 0)
used[i] = 1, k--, sum ^= i;
return sum;
}
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], bb[N * 2], pp[N * 2], kk[N];
int n, r, p, p_, i, i_, a;
scanf("%d%d", &n, &r);
for (i = 0; i < n * 2; i++)
scanf("%d", &aa[i]), aa[i]--;
i_ = -1, p_ = n * 2;
for (i = 0; i < n * 2; i++) {
int tmp;
if (i > 0)
tmp = aa[i], aa[i] = aa[i - 1], aa[i - 1] = tmp;
memcpy(bb, aa, n * 2 * sizeof *aa);
for (p = 0; p < n * 2; p++)
pp[aa[p]] = p / 2;
if (aa[i] == 0)
p = 0;
else if (aa[i] >= n + 1) {
memset(kk, 0, n * sizeof *kk), kk[0]++;
for (a = n * 2 - 1; a > aa[i]; a--)
kk[pp[a]]++;
p = solve_losers(kk, n), kk[pp[aa[i]]]++, p ^= solve_losers(kk, n);
} else {
memset(kk, 0, n * sizeof *kk);
for (a = 0; a < aa[i]; a++)
kk[pp[a]]++;
p = solve_winners(kk, n), kk[pp[aa[i]]]++, p ^= solve_winners(kk, n);
p = (p - r % n + n) % n;
}
if (p_ >= p)
p_ = p, i_ = i / 2;
}
printf("%d\n", i_ + 1);
return 0;
}
