注意开浮点数

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import java.util.Scanner;

public class Main {
	static Scanner sc=new Scanner(System.in);
    public static void main(String[] args) {
    	double t=0;
    	int cnt=0;
    	double distance=1000;
    	while(distance>=1){
    		//相撞时间
    		t=distance/60.0;
    		distance-=t*20;
    		cnt++;
    	}
    	System.out.println(cnt/2);
    }
}