#include <bits/stdc++.h>
using namespace std;
int n, m, k, d = 1000;
int A[200];
int main() {
  cin >> n >> m >> k;
  for (int i = 1; i <= n; i++) {
    cin >> A[i];
    if (A[i] <= k && fabs(i - m) < d && A[i] != 0) {
      d = fabs(i - m);
    }
  }
  cout << d * 10;
}
