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

public class Range {

    static long proveri(long N, long A, long B) {
        long left = A, right = B;
        while(left <= right) {
            long middle = (left + right) / 2;
            long tmp = middle;
            long sum = 0;
            while(tmp > 0) {
                sum += tmp % 10;
                tmp /= 10;
            }
            long resultEquation = middle * middle + 200 * middle + sum;
            if(resultEquation == N) {
                return middle;
            }
            if(resultEquation < N) {
                left = middle + 1;
            }
            else {
                right = middle - 1;
            }

        }
        return -1;
    }

    public static void main(String[] args) throws Exception {
        long 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();

    }

}