#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, k;
  cin >> n >> m >> k;
  int j = 101, t;
  for (int i = 0; i < n; i++) {
    cin >> t;
    if (t <= k && t != 0) {
      j = min(j, abs(i - m + 1));
    }
  }
  cout << j * 10;
  return 0;
}
