#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, k;
  scanf("%d %d %d", &n, &m, &k);
  int a, res = 1e9;
  for (int i = 1; i <= n; ++i) {
    scanf("%d", &a);
    if (a != 0 && a <= k) res = min(res, abs(i - m));
  }
  printf("%d", 10 * res);
  return 0;
}
