#include <bits/stdc++.h>
using namespace std;
int main() {
  long long N, E, T;
  cin >> N >> E >> T;
  vector<long long> x(N), dp(N, 1000000000000);
  dp[0] = T;
  for (int i = 0; i < N; i++) {
    cin >> x[i];
    for (int j = 0; j < i; j++) {
      dp[i] = min(dp[i], dp[j] + max(T, 2 * (x[i] - x[j])));
    }
  }
  cout << dp[N - 1] << endl;
  return 0;
}
