我的gpa专属计算器

import java.util.*;
public class Main{
	static int manner(int sub,int num) {
		int gpa=0,flag;
		if(num<60) {
			gpa=0;
		}
		else if(num>=60&&num<=69) {
			gpa=1;
		}
		else if(num>=70&&num<=79) {
			gpa=2;
		}
		else if(num>=80&&num<=89) {
			gpa=3;
		}
		else if(num>=90&&num<=99) {
			gpa=4;
		}
		else if(num==100) {
			gpa=5;
		}
		flag=sub*gpa;
		return flag;
	}
	public static void main(String[] args) {
		Scanner input=new Scanner(System.in);
		double gpa=0;
		int sum=0;
		int sub,num;
		int n=input.nextInt();
		for(int i=1;i<=n;i++) {
			sub=input.nextInt();
			num=input.nextInt();
			sum=sum+sub;
			gpa=gpa+manner(sub,num);
		}
		System.out.print(String.format("%.1f",gpa/(sum*1.0)));
	}
}