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 s;
        for(long i=A;i<=B;i++){
            s=zbir(i,0);
            if(i*i+s+200*i==N)
                return i;

        }
        return -1;
    }

    static long zbir(long a,long suma){
        if(a==0) return suma;
        return zbir(a/10,suma+a%10);
    }

    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();

    }

}