CodeForces 675A Infinite Sequence（等差数列求项）

http://codeforces.com/problemset/problem/675/A

A. Infinite Sequence

time limit per test
1 second

memory limit per test
256 megabytes

input
standard input

output
standard output

Vasya likes everything infinite. Now he is studying the properties of a sequence s, such that its first element is equal to a (s1 = a),
and the difference between any two neighbouring elements is equal to c (si - si - 1 = c).
In particular, Vasya wonders if his favourite integer bappears in this sequence, that is, there exists a positive integer i,
such that si = b.
Of course, you are the person he asks for a help.

Input

The first line of the input contain three integers a, b and c ( - 109 ≤ a, b, c ≤ 109) —
the first element of the sequence, Vasya's favorite number and the difference between any two neighbouring elements of the sequence, respectively.

Output

If b appears in the sequence s print
"YES" (without quotes), otherwise print "NO" (without
quotes).

Examples

input

1 7 3

output

YES

input

10 10 0

output

YES

input

1 -4 5

output

NO

input

0 60 50

output

NO

Note

In the first sample, the sequence starts from integers 1, 4, 7,
so 7 is its element.

In the second sample, the favorite integer of Vasya is equal to the first element of the sequence.

In the third sample all elements of the sequence are greater than Vasya's favorite integer.

In the fourth sample, the sequence starts from 0, 50, 100,
and all the following elements are greater than Vasya's favorite integer.

题意：

看懂的话就知道这是等差数列求值问题。

思路：

等差数列通项公式 an = a1 + ( n - 1 ) * d ；

对应题目求出的 n 如果是正整数就满足要求。

参考 AC code：

#include<cstdio>
#include<cstring>
const int MYDD=1103;

int main() {
int a,b,c;
while(scanf("%d%d%d",&a,&b,&c)!=EOF) {
if(a==b) {
puts("YES");
continue;
}

if(c!=0) {// c！= 0
int dd2;
double dd1;
dd2=(b-a)/c;
dd1=(b-a)*1.0/(c*1.0);
if((double)dd2!=dd1) puts("NO");
else {
if(dd2>0) puts("YES");
else puts("NO");
}
} else {//防止编译错误
if(a==b) puts("YES");
else puts("NO");
}
}
return 0;
}
/*By: Shyazhut
10 10 42
YES*/