#include <bits/stdc++.h>
int main() {
  int n, m, k, p, d = 100;
  scanf("%d %d %d", &n, &m, &k);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &p);
    if (p > 0 && k >= p && abs(i - m) <= d) d = abs(i - m);
  }
  printf("%d", d * 10);
  return 0;
}
