Problem p03221 (C++)

Buggy submission (status: Runtime Error):
/*Function Template*/
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int mod = 1000000007;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define ALL(a) (a).begin(), (a).end()
#define IOS                                                                    \
  ios::sync_with_stdio(0);                                                     \
  cin.tie(0);                                                                  \
  cout.tie(0);

ll Len(ll n) {
  ll s = 0;
  while (n != 0)
    s++, n /= 10;
  return s;
}

ll Sint(ll n) {
  ll m = 0, s = 0, a = n;
  while (a != 0)
    s++, a /= 10;
  for (ll i = s - 1; i >= 0; i--)
    m += n / ((ll)pow(10, i)) - (n / ((ll)pow(10, i + 1))) * 10;
  return m;
}

ll Svec(vector<ll> v) {
  ll n = 0;
  for (ll i = 0; i < v.size(); i++)
    n += v[i];
  return n;
}

ll GCD(ll a, ll b) {
  ll r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return b;
}

ll LCM(ll a, ll b) {
  ll c = a, d = b, r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return c / b * d;
}

ll Factorial(ll n) {
  ll m = 1;
  while (n >= 1)
    m *= n, n--;
  return m;
}

vector<pair<char, ll>> runlength(string s, vector<pair<char, ll>> p) {
  ll x = 1;
  if (s.size() == 1) {
    p.push_back(pair<char, ll>(s[0], 1));
    return p;
  }
  for (ll i = 0; i < s.size() - 1; i++) {
    if (s[i] == s[i + 1]) {
      x++;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[i], x));
      }
    } else {
      p.push_back(pair<char, ll>(s[i], x));
      x = 1;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[s.size() - 1], x));
      }
    }
  }
  return p;
}

/*↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓*/
int main() {
  ll n, m, a[100000], b[100000];
  cin >> n >> m;
  vector<ll> v[100000];
  rep(i, m) {
    cin >> a[i] >> b[i];
    v[a[i]].push_back(b[i]);
  }
  rep(i, n) { sort(ALL(v[i + 1])); }
  rep(i, m) {
    printf("%012lld\n",
           (ll)(a[i] * 1000000) +
               (lower_bound(ALL(v[a[i]]), b[i]) - v[a[i]].begin()) + 1);
  }
}

Fixed submission:
/*Function Template*/
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int mod = 1000000007;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define ALL(a) (a).begin(), (a).end()
#define IOS                                                                    \
  ios::sync_with_stdio(0);                                                     \
  cin.tie(0);                                                                  \
  cout.tie(0);

ll Len(ll n) {
  ll s = 0;
  while (n != 0)
    s++, n /= 10;
  return s;
}

ll Sint(ll n) {
  ll m = 0, s = 0, a = n;
  while (a != 0)
    s++, a /= 10;
  for (ll i = s - 1; i >= 0; i--)
    m += n / ((ll)pow(10, i)) - (n / ((ll)pow(10, i + 1))) * 10;
  return m;
}

ll Svec(vector<ll> v) {
  ll n = 0;
  for (ll i = 0; i < v.size(); i++)
    n += v[i];
  return n;
}

ll GCD(ll a, ll b) {
  ll r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return b;
}

ll LCM(ll a, ll b) {
  ll c = a, d = b, r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return c / b * d;
}

ll Factorial(ll n) {
  ll m = 1;
  while (n >= 1)
    m *= n, n--;
  return m;
}

vector<pair<char, ll>> runlength(string s, vector<pair<char, ll>> p) {
  ll x = 1;
  if (s.size() == 1) {
    p.push_back(pair<char, ll>(s[0], 1));
    return p;
  }
  for (ll i = 0; i < s.size() - 1; i++) {
    if (s[i] == s[i + 1]) {
      x++;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[i], x));
      }
    } else {
      p.push_back(pair<char, ll>(s[i], x));
      x = 1;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[s.size() - 1], x));
      }
    }
  }
  return p;
}

/*↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓*/
int main() {
  ll n, m, a[100000], b[100000];
  cin >> n >> m;
  vector<ll> v[100001];
  rep(i, m) {
    cin >> a[i] >> b[i];
    v[a[i]].push_back(b[i]);
  }
  rep(i, n) { sort(ALL(v[i + 1])); }
  rep(i, m) {
    printf("%012lld\n",
           (ll)(a[i] * 1000000) +
               (lower_bound(ALL(v[a[i]]), b[i]) - v[a[i]].begin()) + 1);
  }
}