Codeforces Round #318 [RussianCodeCup Thanks-Round] (Div. 2)——A二分——Bear and Elections

/*
贪心WA一发。。二分枚举加的数
赛后发现直接暴力枚举1到1000也是可以的
*/
/************************************************
* Author        :Powatr
* Created Time  :2015-8-30 0:58:45
* File Name     :A.cpp
 ************************************************/

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <cstring>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <bitset>
#include <cstdlib>
#include <ctime>
using namespace std;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
typedef long long ll;
const int MAXN = 1e3 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;

int a[MAXN];
int n;
bool check(int x)
{
    int sum = 0;
    for(int i = 2; i <= n; i++){
        if(a[1] + x <= a[i]){
            sum += a[i] - a[1] - x + 1;
        }
    }
    if(sum <= x) return true;
    return false;
}

int main(){
    while(~scanf("%d", &n)){
        for(int i = 1; i <= n; i++)
            scanf("%d", &a[i]);
        int l = 0, r = 100000;
        int res = 0;
        while(l <= r){
            int mid = l + r >> 1;
            if(check(mid)){
                r = mid - 1;
                res = mid;
            }
            else l = mid + 1;
        }
        printf("%d\n", res);
    }
    return 0;
}