很简单
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner cin = new Scanner(System.in);
int n;
while (cin.hasNext()) {
n=cin.nextInt();
System.out.println(cal(n));
System.out.println();
}
}
public static int cal(int n){
int result=0;
for(int i=1;i<=n;i++){
result+=i;
}
return result;
}
}