<h1 id="heading">题目</h1>
<p>{% fold 点击显/隐题目 %}</p>
<div class="oj"><div class="part" title="Description">
Mister B once received a gift: it was a book about aliens, which he started read immediately. This book had c pages.
<p>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.</p>
<p>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.</p>
<p>Help Mister B to calculate how many days he needed to finish the book.</p>
</div><div class="part" title="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.
</div><div class="part" title="Output">
Print one integer — the number of days Mister B needed to finish the book.
</div><div class="samp"><div class="clear"></div><div class="input part" title="Sample Input">
5 5 10 5 4
12 4 12 4 1
15 1 100 0 0
</div><div class="output part" title="Sample Output">
1
3
15
</div><div class="clear"></div></div></div>
{% endfold %}

<h1 id="heading-1">题解</h1>
<blockquote>
<p><strong>题意</strong><br>
一本有 <code>c</code> 页的书,第一天读 <code>v0</code> 页,每天比前一天多读 <code>a</code> 页(最多不超过 <code>v1</code>)<br>
同时每天需要复习前一天读过的 <code>l</code> 页<br>
问需要几天读完需要多久</p>
</blockquote>
<p>需要注意的是第一天是不需要复习前一天的内容的</p>
<h1 id="heading-2">代码</h1>
<p>{% fold 点击显/隐代码 %}```cpp Mister B and Book Reading <a href="https://github.com/OhYee/sourcecode/tree/master/ACM">https://github.com/OhYee/sourcecode/tree/master/ACM</a> 代码备份<br>
/<em>/<br>
#define debug<br>
#include <ctime><br>
//</em>/<br>
#include <cstdio><br>
#include <cstring><br>
#include <iostream><br>
using namespace std;</p>
<p>int main() {<br>
#ifdef debug<br>
freopen(&quot;in.txt&quot;, &quot;r&quot;, stdin);<br>
int START = clock();<br>
#endif<br>
cin.tie(0);<br>
cin.sync_with_stdio(false);</p>
<pre><code>int c, v0, v1, a, l;

while (cin &gt;&gt; c &gt;&gt; v0 &gt;&gt; v1 &gt;&gt; a &gt;&gt; l) {
    int ans = 0;
    int hr = 0;
    while (hr &lt; c) {
        if(ans)
            hr -= l;
        v0 = min(v0, v1);
        hr += v0;
        ans++;

        v0 += a;
    }
    cout &lt;&lt; ans &lt;&lt; endl;
}
</code></pre>
<p>#ifdef debug<br>
printf(&quot;Time:%.3fs.\n&quot;, double(clock() - START) / CLOCKS_PER_SEC);<br>
#endif<br>
return 0;<br>
}</p>
<pre style="background-color:#fff">{% endfold %}</pre>

Codeforces 820A.Mister B and Book Reading