B. The Queue time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output
Finally! Vasya have come of age and that means he can finally get a passport! To do it, he needs to visit the passport office, but it's not that simple. There's only one receptionist at the passport office and people can queue up long before it actually opens. Vasya wants to visit the passport office tomorrow.
He knows that the receptionist starts working after ts minutes have passed after midnight and closes after tf minutes have passed after midnight (so that (tf - 1) is the last minute when the receptionist is still working). The receptionist spends exactly t minutes on each person in the queue. If the receptionist would stop working within t minutes, he stops serving visitors (other than the one he already serves).
Vasya also knows that exactly n visitors would come tomorrow. For each visitor Vasya knows the point of time when he would come to the passport office. Each visitor queues up and doesn't leave until he was served. If the receptionist is free when a visitor comes (in particular, if the previous visitor was just served and the queue is empty), the receptionist begins to serve the newcomer immediately.
"Reception 1"
For each visitor, the point of time when he would come to the passport office is positive. Vasya can come to the office at the time zero (that is, at midnight) if he needs so, but he can come to the office only at integer points of time. If Vasya arrives at the passport office at the same time with several other visitors, he yields to them and stand in the queue after the last of them.
Vasya wants to come at such point of time that he will be served by the receptionist, and he would spend the minimum possible time in the queue. Help him!
Input
The first line contains three integers: the point of time when the receptionist begins to work ts, the point of time when the receptionist stops working tf and the time the receptionist spends on each visitor t. The second line contains one integer n — the amount of visitors (0 ≤ n ≤ 100 000). The third line contains positive integers in non-decreasing order — the points of time when the visitors arrive to the passport office.
All times are set in minutes and do not exceed 1012; it is guaranteed that ts < tf. It is also guaranteed that Vasya can arrive at the passport office at such a point of time that he would be served by the receptionist.
Output
Print single non-negative integer — the point of time when Vasya should arrive at the passport office. If Vasya arrives at the passport office at the same time with several other visitors, he yields to them and queues up the last. If there are many answers, you can print any of them.
Examples input
10 15 2
2
10 13
output
12 input
8 17 3
4
3 4 5 8
output
2 Note
In the first example the first visitor comes exactly at the point of time when the receptionist begins to work, and he is served for two minutes. At 12 minutes after the midnight the receptionist stops serving the first visitor, and if Vasya arrives at this moment, he will be served immediately, because the next visitor would only come at 13 minutes after midnight.
In the second example, Vasya has to come before anyone else to be served.
題目連結：http://codeforces.com/contest/767/problem/B
比賽卡了我一個小時50分鐘，我想麻煩了，借鑒柏皓的思路，補了一發，這個思路确實簡單。
題目的意思是說，有個人需要辦理一個證件，證件辦理處開門的時間是ta到tb，辦理一個證件需要t的時間，現在有n個人，知道n個人來的時間，求這個辦理證件的人在什麼時間來等待的時間最少。
注意坑點，若最後一個不足t，則不辦理，比如7 14 3 2 1 2 不能輸出13，因為從13開始辦理時間不足t，題目中直說辦理的，我被坑在了這裡，注意long long 。
柏皓的思路很簡潔，因為是非遞減輸入，對于每個輸入我們進行”試插”，即在a-1和a+1兩個地方試試。
代碼：
#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
int main(){
long long a,b,t;
long long m=1e12+10;
cin>>a>>b>>t;
int n;
cin>>n;
long long ans=0;
while(n--){
long long k;
cin>>k;
if(k<=b-t){//注意判斷輸入資料合法
if(k&&max(a,k-1)<=b-t&&(a-k+1)<m){
m=a-k+1;//需要等待的最小時間
ans=min(a,k-1);
}
a=max(a,k)+t;
}
}
if(a<=b-t){//這樣就可以不用等待
ans=a;
}
cout<<ans<<endl;
return 0;
}