import java.io.*;
import java.util.Arrays;
import java.util.StringJoiner;
import java.util.StringTokenizer;
import java.util.function.Function;

public class Main {

    static int N;
    static String S, T;

    public static void main(String[] args) {
        FastScanner sc = new FastScanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        while(true) {
            N = sc.nextInt();
            if( N == 0 ) break;

            S = sc.next();
            T = sc.next();
            pw.println(solve());
        }
        pw.flush();
    }

    static int solve() {
        int[] diff = new int[N];
        for (int i = 0; i < N; i++) {
            int s = S.charAt(i) - '0';
            int t = T.charAt(i) - '0';
            diff[i] = t - s;
            if( diff[i] < 0 ) {
                diff[i] += 10;
            }
        }
        // debug(diff);

        return dfs(0, diff);
    }

    static int dfs(int i, int[] diff) {
        if( i == N ) return 0;

        if( diff[i] == 0 ) {
            return dfs(i+1, diff);

        } else {
            int d = diff[i];
            int ret = Integer.MAX_VALUE;
            // [i, j]をdiff分動かす
            for (int j = i; j < N; j++) {
                for (int k = i; k <= j; k++) {
                    diff[k] = sub(diff[k], d);
                }
                ret = Math.min(ret, dfs(i+1, diff)+1);
                for (int k = i; k <= j; k++) {
                    diff[k] = add(diff[k], d);
                }
            }
            return ret;
        }
    }

    static int MOD = 10;

    static int pow(int base, long exp) {
        if (exp == 0) return 1;

        int ans = 1;
        base %= MOD;
        while (exp > 0) {
            if ((exp & 1) == 1) {
                ans = mul(ans, base);
            }

            base = mul(base, base);
            exp = exp >> 1;
        }
        return ans;
    }

    static int sub(int a, int b) {
        int c = a - b;
        if (c < 0) c += MOD;
        return c;
    }

    static int div(int a, int b) {
        return mul(a, pow(b, MOD - 2));
    }

    static int add(int a, int b) {
        int c = a + b;
        if (c >= MOD) c %= MOD;
        return c;
    }

    static int mul(int a, int b) {
        long c = (long) a * b;
        if (c >= MOD) c %= MOD;
        return (int) c;
    }

    static class FermatCombination {
        private final int size;
        private final int[] factorial; // n -> factorial(n)
        private final int[] inverse;   // n -> inverse(factorial(n))

        FermatCombination(int size) {
            this.size = size;
            factorial = new int[size + 1];
            inverse = new int[size + 1];

            init();
        }

        private void init() {
            factorial[0] = 1;
            factorial[1] = 1;
            inverse[0] = 1;
            inverse[1] = 1;
            for (int i = 2; i <= size; i++) {
                factorial[i] = mul(factorial[i - 1], i);
                inverse[i] = pow(factorial[i], MOD - 2);
            }
        }

        int comb(int n, int k) {
            if (n > size) throw new RuntimeException("wtf : size=" + size + " n=" + n);
            return mul(mul(factorial[n], inverse[k]), inverse[n - k]);
        }

        // 重複組み合わせ
        // k種類からn個選ぶ場合の数
        int hcomb(int k, int n) {
            return comb(k + n - 1, n);
        }

        int group(int n, int g, int k) {
            // C(n, g) * C(n-g, g)... / k!
            // n! / (n-gk)! / g! ^ k / k!
            int ret = factorial[n];             // n!
            ret = mul(ret, inverse[n - g * k]);   // 1 / (n-gk)!
            ret = mul(ret, pow(inverse[g], k)); // 1 / (g! ^ k)
            ret = mul(ret, inverse[k]);         // 1 / k!
            return ret;
        }
    }

    @SuppressWarnings("unused")
    static class FastScanner {
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        FastScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
            tokenizer = null;
        }

        String next() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        String nextLine() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    return reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken("\n");
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        int[] nextIntArray(int n, int delta) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt() + delta;
            return a;
        }

        long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            return a;
        }
    }

    static <A> void writeLines(A[] as, Function<A, String> f) {
        PrintWriter pw = new PrintWriter(System.out);
        for (A a : as) {
            pw.println(f.apply(a));
        }
        pw.flush();
    }

    static void writeLines(int[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (int a : as) pw.println(a);
        pw.flush();
    }

    static void writeLines(long[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (long a : as) pw.println(a);
        pw.flush();
    }

    static int max(int... as) {
        int max = Integer.MIN_VALUE;
        for (int a : as) max = Math.max(a, max);
        return max;
    }

    static int min(int... as) {
        int min = Integer.MAX_VALUE;
        for (int a : as) min = Math.min(a, min);
        return min;
    }

    static void debug(Object... args) {
        StringJoiner j = new StringJoiner(" ");
        for (Object arg : args) {
            if (arg instanceof int[]) j.add(Arrays.toString((int[]) arg));
            else if (arg instanceof long[]) j.add(Arrays.toString((long[]) arg));
            else if (arg instanceof double[]) j.add(Arrays.toString((double[]) arg));
            else if (arg instanceof Object[]) j.add(Arrays.toString((Object[]) arg));
            else j.add(arg.toString());
        }
        System.err.println(j.toString());
    }
}



Measured memory_bytes: 25612