#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <sstream>
#include <complex>
#include <ctime>
#include <cassert>
#include <functional>

using namespace std;

typedef long long ll;
typedef vector<int> VI;
typedef pair<int,int> PII;

#define REP(i,s,t) for(int i=(s);i<(t);i++)
#define FILL(x,v) memset(x,v,sizeof(x))

const int INF = (int)1E9;

int main() {
  int n, d, c;
  cin >> n >> d >> c;
  VI b(n);
  REP(i,0,n) cin >> b[i];
  int l = 0, r = d;
  while (l <= r) {
    int m = (l + r) / 2, cur = c;
    bool ok = true;
    REP(i,0,n) {
      if (b[i] < m) {
        cur -= m - b[i];
        if (cur < 0) {
          ok = false;
          break;
        }
      }
      else cur += min(b[i] - m, c - cur);
    }
    if (ok) l = m + 1;
    else r = m - 1;
  }
  int lo = r;

  l = 0; r = d;
  while (l <= r) {
    int m = (l + r) / 2, cur = 0;
    bool ok = true;
    REP(i,0,n) {
      if (b[i] > m) {
        cur += b[i] - m;
        if (cur > c) {
          ok = false;
          break;
        }
      }
      else cur -= min(m - b[i], cur);
    }
    if (ok) r = m - 1;
    else l = m + 1;
  }
  int hi = l;

  cout << max(0, hi - lo) << endl;
  return 0;
}