CF＃421 A. Mister B and Book Reading（模拟）

A. Mister B and Book Reading

time limit per test
2 seconds

memory limit per test
256 megabytes

input
standard input

output
standard output

Mister B once received a gift: it was a book about aliens, which he started read immediately. This book had c pages.

At first day Mister B read v0 pages,
but after that he started to speed up. Every day, starting from the second, he read a pages more than on the previous day (at first
day he read v0 pages,
at second — v0 + a pages,
at third — v0 + 2a pages,
and so on). But Mister B is just a human, so he physically wasn't able to read more than v1 pages
per day.

Also, to refresh his memory, every day, starting from the second, Mister B had to reread last l pages he read on the previous day.
Mister B finished the book when he read the last page for the first time.

Help Mister B to calculate how many days he needed to finish the book.

Input

First and only line contains five space-separated integers: c, v0, v1, a and l (1 ≤ c ≤ 1000, 0 ≤ l < v0 ≤ v1 ≤ 1000, 0 ≤ a ≤ 1000)
— the length of the book in pages, the initial reading speed, the maximum reading speed, the acceleration in reading speed and the number of pages for rereading.

Output

Print one integer — the number of days Mister B needed to finish the book.

Examples

input

5 5 10 5 4

output

1

input

12 4 12 4 1

output

3

input

15 1 100 0 0

output

15

Note

In the first sample test the book contains 5 pages, so Mister B read it right at the first day.

In the second sample test at first day Mister B read pages number 1 - 4, at second day — 4 - 11,
at third day — 11 - 12 and finished the book.

In third sample test every day Mister B read 1 page of the book, so he finished in 15 days.

模拟一下就出来了

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <string.h>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <list>
#include <bitset>
#include <stack>
#include <stdlib.h>
#define lowbit(x) (x&-x)
#define e exp(1.0)
#define eps 1e-8
//ios::sync_with_stdio(false);
// auto start = clock();
// cout << (clock() - start) / (double)CLOCKS_PER_SEC<<endl;
typedef long long ll;
typedef long long LL;
using namespace std;
typedef unsigned long long ull;
int main()
{
ios::sync_with_stdio(false);
int c,v0,v1,a,l,ans;
while(cin>>c>>v0>>v1>>a>>l)
{
ans=0;
int n=c;
int v;
while(n>0)
{
if(ans!=0) n=n+l;
v=min(v0+a*ans,v1);
n=n-v;
ans++;
}
cout<<ans<<endl;
}
return 0;
}