#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,mmx,tune=native")
#pragma comment(linker, "/STACK:256000000")
using namespace std;
mt19937 rd(
    (unsigned int)chrono::steady_clock::now().time_since_epoch().count());
const int INF = 1000 * 1000 * 1000 + 322;
const long long LLINF =
    2LL * 1000LL * 1000LL * 1000LL * 1000LL * 1000LL * 1000LL + 57;
constexpr unsigned int MOD = 1000 * 1000 * 1000 + 7;
constexpr unsigned int FFT_MOD = 998244353;
const int P1E6 = 1336337;
const int P1E3 = 1009;
const long long P1E14 = 100000000000031;
const long long P1E17 = 100000000000000003;
const long double PI = acosl(-1.);
const long double EPS = 1e-9;
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const pair<T, U> &_p) {
  _out << _p.x << " " << _p.y;
  return _out;
}
template <typename T, typename U>
inline istream &operator>>(istream &_in, pair<T, U> &_p) {
  _in >> _p.x >> _p.y;
  return _in;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const vector<T> &_v) {
  if (_v.empty()) return _out;
  _out << _v.front();
  for (auto _it = ++_v.begin(); _it != _v.end(); ++_it) _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline istream &operator>>(istream &_in, vector<T> &_v) {
  for (auto &_i : _v) _in >> _i;
  return _in;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const set<T> &_s) {
  if (_s.empty()) return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const multiset<T> &_s) {
  if (_s.empty()) return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const unordered_set<T> &_s) {
  if (_s.empty()) return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const unordered_multiset<T> &_s) {
  if (_s.empty()) return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) _out << ' ' << *_it;
  return _out;
}
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const map<T, U> &_m) {
  if (_m.empty()) return _out;
  _out << '(' << _m.begin()->x << ": " << _m.begin()->y << ')';
  for (auto _it = ++_m.begin(); _it != _m.end(); ++_it)
    _out << ", (" << _it->x << ": " << _it->y << ')';
  return _out;
}
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const unordered_map<T, U> &_m) {
  if (_m.empty()) return _out;
  _out << '(' << _m.begin()->x << ": " << _m.begin()->y << ')';
  for (auto _it = ++_m.begin(); _it != _m.end(); ++_it)
    _out << ", (" << _it->x << ": " << _it->y << ')';
  return _out;
}
const char *infile = "";
const char *outfile = "";
inline long long gcd(long long a, long long b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
inline long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
inline int pwm(long long xx, long long pow, int MD) {
  if (pow < 0) {
    pow = pow % (MD - 1) + MD - 1;
  }
  long long mlt = 1;
  while (pow) {
    if (pow & 1) {
      mlt *= xx;
      mlt %= MD;
    }
    xx *= xx;
    pow >>= 1;
    xx %= MD;
  }
  return (int)mlt;
}
inline long long gcdex(long long a, long long b, long long &x, long long &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  long long xx, yy;
  long long gc = gcdex(b, a % b, yy, xx);
  x = xx;
  y = yy - (a / b) * xx;
  return gc;
}
inline int inv(long long r, int _mod) { return pwm(r % _mod, _mod - 2, _mod); }
inline void solve() {
  int n;
  cin >> n;
  string ans = string(n, '0');
  string u = string(n, '0');
  int m;
  cin >> m;
  for (int i = 0; i < m; ++i) {
    int a, b;
    cin >> a >> b;
    --a;
    if (u[a] != '0') {
      cout << -1 << '\n';
      return;
    }
    ans[a] = b + '0';
    u[a] = '1';
  }
  if (u[0] == '1' && ans[0] == '0') {
    cout << -1 << '\n';
    return;
  }
  if (n == 1 || u[0] == '1') {
    cout << ans << '\n';
    return;
  }
  ans[0] = '1';
  cout << ans << '\n';
}
int main() {
  if (*infile != '\0') (void)freopen(infile, "r", stdin);
  if (*outfile != '\0') (void)freopen(outfile, "w", stdout);
  cout.tie(nullptr);
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  cout << setprecision(20);
  cout << fixed;
  solve();
  return 0;
}
