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

public class Range {

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

    static long ravenka(long x)
    {
        return x*x + s(x) + 200*x;
    }

    static long proveri(long n, long a, long b) {
        //  x^2+s(x)+200*x=N
        long rmax = ravenka(b);
        if (rmax < b)
            return -1;
        else if (rmax == b)
            return b;
        if (ravenka(b/2) < n)
        {
            a = b/2;
        }

        for (long x = a; x <= b; x++)
        {
            long rav = ravenka(x);
            if (rav > n)
            {
                return -1;
            }
            if (rav == n)
            {
                return (int)x;
            }
        }
        return -1;
    }

    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();

    }

}