#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define VRSORT(v) sort(v.begin(), v.end(),greater<int>());
#define INF 999999999
#define MOD 1000000007
#define M_PI 3.14159265358979323846
#define ALL(X) (X).begin(),(X).end()

#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 0};
int dy[]={0, 1, 0, -1, 0};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
 
std::string pad(int num){ char buffer[4]; std::snprintf(buffer, sizeof(buffer), "%03d", num); return buffer;}
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }


int N,M;
vector<int> A,B;

void input(){
  fast_io();
  #ifdef __LOCAL
    fs::path p = __FILE__;
    fs::path input,output;
    input = output = p.parent_path();
    input += string("/input/") + string(p.stem()) + string(".txt");
    output += string("/output/") + string(p.stem()) + string(".txt");
    freopen(input.c_str(), "r", stdin);
    freopen(output.c_str(), "w", stdout);
  #endif
  cin >> N >> M;
  // A.assign(N,0);
  // B.assign(N,0);
  REP(i,N){
    int a,b;
    cin >> a >> b;
    if(a>M) continue;
    A.push_back(a);
    B.push_back(b);
  }
  N = A.size();
}

int solve(){
  input();
  priority_queue<pii,vector<pii>, greater<pii>> pq_0;
  priority_queue<pii> pq_1;
  REP(i,N) pq_0.push({A[i],B[i]});
  ll ans=0;
  // while(!pq_0.empty()){
    // int a,b,tmp_a;
    // tmp_a = a = pq_0.top().first;
    // while(!pq_0.empty()){
    //   tie(a,b) = pq_0.top();
    //   if(tmp_a!=a) break;
    //   pq_1.push({b,a});
    //   pq_0.pop();
    //   tmp_a = a;
    // }
    // for(int i=M-tmp_a;i>=max(M-a,0);i--){
    //   if(pq_1.empty()) continue;
    //   ans += pq_1.top().first;
    //   pq_1.pop();
    // }
  // }
  for(int i=1;i<=M;i++){
    int a,b;
    while(!pq_0.empty()){
      tie(a,b) = pq_0.top();
      if(a>i) break;
      pq_0.pop();
      pq_1.push({b,a});
    }
    if(!pq_1.empty()){
      ans += pq_1.top().first;
      pq_1.pop();
    }
  }
  cout << ans << endl;
  return 0;
}

int main()
{
  solve();
  return 0;
}


Measured memory_bytes: 3312