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															+package main 
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															+ 
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															+import ( 
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															+	"fmt" 
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															+	"math" 
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															+) 
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															+ 
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															+func main() { 
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															+	var n int 
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															+	fmt.Scan(&n) 
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															+	sieve := make([]bool, n+1) 
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															+	prime := make([]int, 0) 
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															+	sqrt := int(math.Sqrt(float64(n))) 
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															+	for i := 2; i <= sqrt; i++ { 
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															+		if sieve[i] { 
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															+			continue 
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															+		} 
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															+		for j := 2 * i; j <= n; j += i { 
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															+			sieve[j] = true 
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															+		} 
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															+	} 
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															+	for i := 2; i <= n; i++ { 
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															+		if !sieve[i] { 
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															+			prime = append(prime, i) 
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															+		} 
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															+	} 
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															+	cnt := 0 
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															+	m := make(map[int]bool) 
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															+	for _, p := range prime { 
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															+		if m[n-p] || 2*p == n { 
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															+			cnt++ 
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															+		} 
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															+		m[p] = true 
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															+	} 
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															+	fmt.Println(cnt) 
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															+} 
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