JAGContest2016DomesticB.java

import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;
 
public class Main {
	public static int  N,X;
	public static boolean arr[];
	public static void main(String[] args) {
		FastScanner sc=new FastScanner();
		int n=sc.nextInt();
		int m=sc.nextInt();
		int t=sc.nextInt();
		int arr[]=new int[n];
		for(int i=0;i<n;i++){
			arr[i]=sc.nextInt();
		}
		int ans=0;
		if(arr[0]>m){
			ans+=arr[0]-m;
		}
		for(int i=0;i<n-1;i++){
			if(arr[i+1]-arr[i]>2*m){
				ans+=arr[i+1]-arr[i]-2*m;
			}
		}
		if(t-arr[n-1]>m){
			ans+=t-arr[n-1]-m;
		}
		System.out.println(ans);
	}
 
 
}
 
class ryori implements Comparable<ryori>{
	public int t,a;
 
	public ryori(int t, int a) {
		super();
		this.t = t;
		this.a = a;
	}
	/*public int compareTo(ryori other){
		int value= other.a-this.a;
		if(value==0){
			return this.t-other.t;
		}else{
			return value;
		}
	}*/
	/*public int compareTo(ryori other){
		int value= this.t-other.t;
		if(value==0){
			return other.a-this.a;
		}else{
			return value;
		}
	}*/
	public int compareTo(ryori other){
		return other.a-this.a;
	}
 
}
 
class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
    public boolean hasNext() { skipUnprintable(); return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        if (!hasNext()) throw new NoSuchElementException();
        int n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
}