Опсег [АПС Вежби за прв колоквиум]

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Range {

    static long cifri(long x) {
        long zbir =0;
        while (x>0) {
            zbir+= x%10;
            x/=10;
        }
        return zbir;
    }

    static long proveri(long N, long A, long B) {

        if (A == B)
            return -1;


        if (A * A + 200*A + cifri(A) == N)
            return A;
        if (B*B + 200*B + cifri(B) == N )
            return B;

        long mid = (A+B)/2;

       // System.out.println(A + " " + B + " " + mid);

        long temp = mid * mid + 200 * mid + cifri(mid);
        if (temp > N)
            return proveri(N,A,mid);
        else  if (temp < N)
            return proveri(N,mid,B);
        else return mid;

    }


    public static void main(String[] args) throws Exception {
        int i,j,k;

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        long N = Long.parseLong(br.readLine());

        StringTokenizer st = new StringTokenizer(br.readLine());
        long A = Long.parseLong(st.nextToken());
        long B = Long.parseLong(st.nextToken());

        long res = proveri(N, A, B);
        System.out.println(res);

        br.close();

    }

}