public class Loop

{

public static void main(String[]args)

{

int sum = 0;

int m = 20;

int n = 100;

int h = (n - m + 1);

System.out.println("m+...+n的和为:" + (m+n)*h/2);

while(m <= n)

{

sum = sum + m;

m++;

}

System.out.println("m+...+n的和为:" + sum);

}

}