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Three poles stand evenly spaced along a line. Their heights are a, b and c meters, from left to right. We will call the arrangement of the poles beautiful if the tops of the poles lie on the same line, that is, b-a = c-b.

Determine whether the arrangement of the poles is beautiful.

Constraints

• 1 \leq a,b,c \leq 100
• a, b and c are integers.

Input

Input is given from Standard Input in the following format:

a b c

Output

Print YES if the arrangement of the poles is beautiful; print NO otherwise.

Examples

Input

2 4 6

Output

YES

Input

2 5 6

Output

NO

Input

3 2 1

Output

YES

inputFormat

Input

Input is given from Standard Input in the following format:

a b c

outputFormat

Output

Print YES if the arrangement of the poles is beautiful; print NO otherwise.

Examples

Input

2 4 6

Output

YES

Input

2 5 6

Output

NO

Input

3 2 1

Output

YES

样例

2 5 6

NO