2 seconds
256 megabytes
standard input
standard output
Valeric and Valerko missed the last Euro football game, so they decided to watch the game's key moments on the Net. They want to start watching as soon as possible but the connection speed is too low. If they turn on the video right now, it will "hang up" as
the size of data to watch per second will be more than the size of downloaded data per second.
The guys want to watch the whole video without any pauses, so they have to wait some integer number of seconds for a part of the video to download. After this number of seconds passes, they can
start watching. Waiting for the whole video to download isn't necessary as the video can download after the guys started to watch.
Let's suppose that video's length is c seconds and Valeric and Valerko wait t seconds
before the watching. Then for any moment of time t0, t ≤ t0 ≤ c + t,
the following condition must fulfill: the size of data received in t0 seconds
is not less than the size of data needed to watch t0 - t seconds
of the video.
Of course, the guys want to wait as little as possible, so your task is to find the minimum integer number of seconds to wait before turning the video on. The guys must watch the video without pauses.
The first line contains three space-separated integers a, b and c (1 ≤ a, b, c ≤ 1000, a > b).
The first number (a) denotes the size of data needed to watch one second of the video. The second number (b)
denotes the size of data Valeric and Valerko can download from the Net per second. The third number (c) denotes the video's length in seconds.
Print a single number — the minimum integer number of seconds that Valeric and Valerko must wait to watch football without pauses.
4 1 1
3
10 3 2
5
13 12 1
1
In the first sample video's length is 1 second and it is necessary 4 units of data for watching 1 second of video, so guys should download 4 · 1 =
4 units of data to watch the whole video. The most optimal way is to wait 3 seconds till 3 units of data will be downloaded and then start watching. While guys will be watching video 1 second, one unit of data will be downloaded and Valerik and Valerko will
have 4 units of data by the end of watching. Also every moment till the end of video guys will have more data then necessary for watching.
In the second sample guys need 2 · 10 = 20 units of data, so they have to wait 5 seconds and after that they will have 20 units before the second second
ends. However, if guys wait 4 seconds, they will be able to watch first second of video without pauses, but they will download 18 units of data by the end of second second and it is less then necessary.
解题说明：此题需要搞清三个变量的关系，a是指观看视频每秒必须要这么多流量，b是指下载流量，c是指视频时长。由于可以边下载边观看，为了保证不卡，需要确保(a-b)*c这些视频必须要提前下载好，否则在观看时a比b大肯定无法及时下载，同时还要加上刚开始下载b流量的一秒时长。至于式子中减去1的操作是为做除法时调整误差。
#include <cstdio>
#include<iostream>
using namespace std;
int main()
{
int a,b,c;
scanf("%d %d %d",&a,&b,&c);
printf("%d\n",((a-b)*c+b-1)/b);
return 0;
}