Language: C++

 #include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <cctype>
#include <cassert>
#include <climits>
#include <string>
#include <bitset>
#include <cfloat>
#include <unordered_set>
#include <iomanip>
using namespace std;
typedef long double ld;
typedef long long int ll;
typedef unsigned long long int ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<char> vc;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef vector<string> vs;
typedef vector<ll> vll;
typedef vector<pair<int,int> > vpii;
typedef vector<vector<int> > vvi;
typedef vector<vector<char> > vvc;
typedef vector<vector<string> > vvs;
typedef vector<vector<ll> > vvll;
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define irep(it, stl) for(auto it = stl.begin(); it != stl.end(); it++)
#define drep(i,n) for(int i = (n) - 1; i >= 0; --i)
#define fin(ans) cout << (ans) << endl
#define mp(p,q) make_pair(p, q)
#define pb(n) push_back(n)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define Sort(a) sort(a.begin(), a.end())
#define Rort(a) sort(a.rbegin(), a.rend())
#define MATHPI acos(-1)
int dx8[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy8[8] = {0, 1, 0, -1, 1, 1, -1, -1};
int dx4[4] = {1, 0, -1, 0};
int dy4[4] = {0, 1, 0, -1};
template <class T> inline bool chmax(T& a,T b){if(a<b){a=b;return 1;} return 0;}
template <class T> inline bool chmin(T& a,T b){if(a>b){a=b;return 1;} return 0;}
template<typename A, size_t N, typename T> void Fill(A (&array)[N], const T &val){ fill((T*)array, (T*)(array+N), val); }

struct io{io(){ios::sync_with_stdio(false);cin.tie(0);}};
const int INF = INT_MAX;
const ll LLINF = 1LL<<60;
const ll MOD = 1000000007;
const double EPS = 1e-9;


int main(void){
  int N,M;
  cin >> N >> M;
  int P[100100];
  int Y[100100];
  rep(i,M){
      cin >> P[i] >> Y[i];
      P[i]--;
  }

  vvi vals(N);
  rep(i,M) vals[P[i]].push_back(Y[i]);
  //県ごとの情報を集めてる
  //vals[0] = [32,12],vals[1] = [63]

  rep(i,N){
      //vals[0]を例とすると
        Sort(vals[i]);//[12,32]
        vals.erase(unique(vals[i].begin(),vals[i].end()),vals[i].end());
  }

  rep(i,M){
      int v = P[i];//1つ目の市、p[0]=1県、Y[0]=32の時
      printf("%06d",v+1);//Pは--してたので

      int id = lower_bound(vals[i].begin(),vals[i].end(),Y[i])-vals[i].begin();
      printf("%06d",id+1);//lowerboundは境界の満たさない側の値なので+1
  }

}

Compiler output:
a.cc: In function 'int main()':
a.cc:80:19: error: no matching function for call to 'std::vector<std::vector<int> >::erase(__gnu_cxx::__normal_iterator<int*, std::vector<int> >, std::vector<int>::iterator)'
   80 |         vals.erase(unique(vals[i].begin(),vals[i].end()),vals[i].end());
      |         ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:5:
/usr/include/c++/14/bits/stl_vector.h:1536:7: note: candidate: 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::erase(const_iterator) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; iterator = std::vector<std::vector<int> >::iterator; const_iterator = std::vector<std::vector<int> >::const_iterator]'
 1536 |       erase(const_iterator __position)
      |       ^~~~~
/usr/include/c++/14/bits/stl_vector.h:1536:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:1564:7: note: candidate: 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::erase(const_iterator, const_iterator) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; iterator = std::vector<std::vector<int> >::iterator; const_iterator = std::vector<std::vector<int> >::const_iterator]'
 1564 |       erase(const_iterator __first, const_iterator __last)
      |       ^~~~~
/usr/include/c++/14/bits/stl_vector.h:1564:28: note:   no known conversion for argument 1 from '__normal_iterator<int*,vector<int>>' to '__normal_iterator<const std::vector<int>*,vector<std::vector<int>>>'
 1564 |       erase(const_iterator __first, const_iterator __last)
      |             ~~~~~~~~~~~~~~~^~~~~~~