Language: Java

import java.io.*;
import java.util.*;

class s967693306 {
    static final long INF = Long.MAX_VALUE / 2;
    static final int MOD = 1_000_000_007;
    static final int SIZE = 1_000_000;
    long[] fac = new long[SIZE];
    long[] inv = new long[SIZE];
    long[] finv = new long[SIZE];
    FastScanner sc = new FastScanner();

    public static void main(String[] args) {
        new s967693306().solve();
    }

    void solve() {

        int n = sc.nextInt();
        int m = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();

        for (int i = 0; i < m; i++) {
            int s = sc.nextInt();
            int c = sc.nextInt();
            if (map.get(s) != null && map.get(s) != c) {
                System.out.println(-1);
                System.exit(0);
            }
            map.put(s, c);
        }

        for (int i = 0; i < 1000; i++) {
            String s = "" + i;
            boolean flag = true;
            if (s.length() < n) continue;
            for (int j = 0; j < n; j++) {
                if ((map.get(j + 1) != null
                                && map.get(j + 1) != Character.getNumericValue(s.charAt(j)))
                        || (map.get(j + 1) == null
                                && Character.getNumericValue(s.charAt(j)) != 0)) {
                    if (map.get(j + 1) == null
                            && j == 0
                            && Character.getNumericValue(s.charAt(j)) == 1) {
                        continue;
                    }
                    flag = false;
                    break;
                }
            }
            if (flag && s.length() == n) {
                System.out.println(s);
                System.exit(0);
            }
        }

        System.out.println(-1);
    }

    long gcd(long a, long b) {
        if (b == 0) {
            return a;
        }
        return gcd(b, a % b);
    }

    long lcm(long a, long b) {
        return a * b / gcd(a, b);
    }

    long inv(long a) {
        return pow(a, MOD - 2);
    }

    long pow(long a, long r) {
        long sum = 1;
        while (r > 0) {
            if ((r & 1) == 1) {
                sum *= a;
                sum %= MOD;
            }
            a *= a;
            a %= MOD;
            r >>= 1;
        }
        return sum;
    }

    long modFact(long n) {
        if (n == 0) {
            return 1;
        }
        return n * modFact(n - 1) % MOD;
    }

    long fact(long n) {
        if (n == 0) {
            return 1;
        }
        return n * fact(n - 1);
    }

    void initCOMB() {
        fac[0] = fac[1] = 1;
        inv[1] = 1;
        finv[0] = finv[1] = 1;
        for (int i = 2; i < SIZE; i++) {
            fac[i] = fac[i - 1] * i % MOD;
            inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
            finv[i] = finv[i - 1] * inv[i] % MOD;
        }
    }

    long modComb(int n, int r) {
        if (n < r || n < 0 || r < 0) return 0;
        return fac[n] * finv[r] % MOD * finv[n - r] % MOD;
    }

    long comb(long n, long r) {
        long num = 1;
        for (long i = 1; i <= r; i++) {
            num = num * (n - i + 1) / i;
        }
        return num;
    }

    boolean isPrime(long a) {
        if (a <= 1) return false;
        for (int i = 2; i * i <= a; i++) {
            if (a % i == 0) return false;
        }
        return true;
    }

    String nextPermutation(String s) {
        ArrayList<Character> list = new ArrayList<>();
        for (int i = 0; i < s.length(); i++) list.add(s.charAt(i));

        int pivotPos = -1;
        char pivot = 0;
        for (int i = list.size() - 2; i >= 0; i--) {
            if (list.get(i) < list.get(i + 1)) {
                pivotPos = i;
                pivot = list.get(i);
                break;
            }
        }

        if (pivotPos == -1 && pivot == 0) return null;

        int L = pivotPos + 1;
        int R = list.size() - 1;
        int minPos = -1;
        char min = Character.MAX_VALUE;
        for (int i = R; i >= L; i--) {
            if (pivot < list.get(i)) {
                if (list.get(i) < min) {
                    min = list.get(i);
                    minPos = i;
                }
            }
        }

        Collections.swap(list, pivotPos, minPos);
        Collections.sort(list.subList(L, R + 1));

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < list.size(); i++) sb.append(list.get(i));

        return sb.toString();
    }

    boolean nextPermutation(long[] a) {
        for (int i = a.length - 1; i > 0; i--) {
            if (a[i - 1] < a[i]) {
                int swapIndex = find(a[i - 1], a, i, a.length - 1);
                long temp = a[swapIndex];
                a[swapIndex] = a[i - 1];
                a[i - 1] = temp;
                Arrays.sort(a, i, a.length);
                return true;
            }
        }
        return false;
    }

    int find(long dest, long[] a, int s, int e) {
        if (s == e) {
            return s;
        }
        int m = (s + e + 1) / 2;
        return a[m] <= dest ? find(dest, a, s, m - 1) : find(dest, a, m, e);
    }

    void elimination(int[][] a, int[] b) {
        int n = a.length;
        double f;
        for (int k = 0; k < n - 1; k++) {
            for (int i = k + 1; i < n; i++) {
                f = -a[i][k] / a[k][k];
                for (int j = k + 1; j < n; j++) {
                    a[i][j] += f * a[k][j];
                }
                b[i] += f * b[k];
            }
            for (int i = n - 1; i >= 0; i--) {
                for (int j = i + 1; j < n; j++) {
                    b[i] -= a[i][j] * b[j];
                }
                b[i] = b[i] / a[i][i];
            }
        }
    }
}

class Pair implements Comparable<Pair> {
    long a, b;

    public Pair(long i, long j) {
        a = i;
        b = j;
    }

    @Override
    public int compareTo(Pair p) {
        if (this.b < p.b) return -1;
        else if (this.b > p.b) return 1;
        else return 0;
    }
}

class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;

    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        } else {
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }

    private int readByte() {
        if (hasNextByte()) return buffer[ptr++];
        else return -1;
    }

    private static boolean isPrintableChar(int c) {
        return 33 <= c && c <= 126;
    }

    public boolean hasNext() {
        while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
        return hasNextByte();
    }

    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while (isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while (true) {
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            } else if (b == -1 || !isPrintableChar(b)) {
                return minus ? -n : n;
            } else {
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }

    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }
}


Example test case(s):
input: 3 3
1 7
3 2
1 7

output: 702