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

public class Range {

    static int proveri(double N, long A, long B) {
         if(B-A<10000000)
        {
             //System.out.println(A);
             ///System.out.println(B);
                /*if( (B*B+zbirCifri(B)+200*B==N) || (A*A+zbirCifri(A)+200*A==N) )
                {
                        if(B*B+zbirCifri(B)+200*B==N)
                                System.out.println(B);
                        if(A*A+zbirCifri(A)+200*A==N)
                                System.out.println(A);
                        return 1;
                }

                else
                        return -1;
                */
             //int k=0;
             for(long i=A;i<=B;i++)
             {
                 //System.out.println("Forr");
                 double k = i;
                 if(k*k+zbirCifri(i)+200*k==N)
                     return (int)i;
             }
                 return -1;
        }
        else
        {
                double n=(B+A)/2;
                if((n<A)&&(n>B))
                        return -1;
                if(n*n+zbirCifri((long)n)+200*n==N)
                {
                        System.out.println(n);
                        System.out.println("Dolu");
                        return 1;


                }
                else if(n*n+zbirCifri((long)n)+200*n<N)
                        return proveri(N, (long)n+1,B);
                else
                        return proveri(N, A,(long)n);

        }
        // Vasiot kod tuka
    }
    static long zbirCifri(long x)
    {
        long sum=0;
        while(x>0)
        {
                sum+=x%10;
                x/=10;
        }
        return sum;
    }

        // Vasiot kod tuka

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

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

        double N = Double.parseDouble(br.readLine());

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

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

        br.close();

    }

}