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本题很简单主要考察的是对int long类型的限制问题
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算法
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
int n = new Scanner(System.in).nextInt();
System.out.println((long)n*(n+1)/2);
}
}
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int 长度限制是10位
long 长度限制是19位