#include <bits/stdc++.h>
int min(int x, int y) { return x < y ? x : y; }
using namespace std;
int main() {
  int n, m, a, k;
  long res = 10000000;
  cin >> n >> m >> k;
  for (int i = 1; i <= n; i++) {
    cin >> a;
    if (a <= k && a != 0) {
      res = min(abs(i - m), res);
    }
  }
  cout << 10 * res;
  return 0;
}
