#include <bits/stdc++.h>
using namespace std;
int abs(int x) {
  if (x < 0)
    return -x;
  else
    return x;
}
int a[110];
int main() {
  int n, m, k, i, j, min, index;
  cin >> n >> m >> k;
  for (i = 1; i <= n; i++) {
    cin >> a[i];
  }
  min = 200;
  for (i = 1; i <= n; i++) {
    if (a[i] == 0 || a[i] > k)
      continue;
    else {
      if (abs(m - i) < min) {
        min = abs(m - i);
      }
    }
  }
  cout << min * 10 << endl;
  return 0;
}
