https://www.acmicpc.net/problem/2438
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
String s = "*";
for(int i = 0; i < n; i++){
for(int j = 0; j < i+1; j++) System.out.print(s);
System.out.print("\n");
}
}
}