题解 | #等差数列#
等差数列
https://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Main {
public static void main(String[] args) throws IOException {
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader bufferedReader = new BufferedReader(isr);
String input = bufferedReader.readLine();
Integer lastNum = Integer.parseInt(input);
int result = 0;
for (int i = 0; i < lastNum; i++) {
result +=(2+3*i);
}
System.out.print(result);
}
}
