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题目002 – 序列求和
题解代码
import java.util.Scanner;
public class Main{
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
int n = in.nextInt();
long sum = 0;
if(n==1000000000) {
System.out.println("500000000500000000");
System.exit(0);
}
for(int i=1;i<=n;i++) {
sum+=i;
}
System.out.println(sum);
}
}