import java.util.Scanner;
public class Main{
public static void main (String[]args){
Scanner sc = new Scanner (System.in);
System.out.print ("请输入一个正整数: ");
int n = sc.nextInt ();
int sum = 0;
for (int i = 1; i <= n; i++){
sum += i;
}
System.out.print (sum);
}
}
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