알고리즘60 :: BOJ_1748_수이어쓰기1

 
import java.io.BufferedReader;
import java.io.InputStreamReader;
 
public class 수이어쓰기1 {
 
    static int n;
    public static void main(String[] args) throws Exception{
        // TODO Auto-generated method stub
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        n = Integer.parseInt(br.readLine());
        
        int init = 10;
        int ans = 0;
        int index = 1;
        int start = 1;
        while(true) {    
            if(init>n) { //마지막
                ans += (n-init/10+1)*index; 
                break;
            }else {
                ans += ((init-1)-start+1) *index;
                init *= 10;
                start *= 10;
                index +=1;
//길이를 세어준다. 
//120
//1~9 = ((10-1)-1+1)*1
//10~99 = ((100-1)-10+1)*2
//100~120 = (120-100+1)*3
            }
        }//end of while loop
        System.out.println(ans);
    }
}