Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		n, m := io.NextInt(), io.NextInt()
		if n == 0 {
			break
		}
		p := make([][]int, m)
		for i := 0; i < n; i++ {
			d, v := io.NextInt()-1, io.NextInt()
			p[d] = append(p[d], v)
		}
		sum := 0
		for i := 0; i < m; i++ {
			max := 0
			for _, v := range p[i] {
				max = intMax(v, max)
			}
			sum += max
		}
		io.Println(sum)
	}
}

func intMax(a, b int) int {
	if a < b {
		return b
	}
	return a
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <bits/stdc++.h>
using namespace std;

#define Int long long int
#define REP(i,n) for(int i=0;i<(n);i++)
#define REAP(i,a,n) for(int i=(a);i<(n);i++)
#define YES cout<<"Yes"<<endl
#define NO cout<<"No"<<endl
#define fr first
#define sc second
#define pb push_back
#define All(v) v.begin(),v.end()

int main(){
    int n,m;
    while(cin >> n >> m,n){
        vector<pair<int,int> > qes(n);
        REP(i,n)cin >> qes[i].first >> qes[i].second;
        sort(All(qes));
        reverse(All(qes));
        int sum=0;
        vector<int> table(m,0);
        REP(i,n){
            if(table[qes[i].first-1]==0){
                sum+=qes[i].second;
                table[qes[i].first-1]=1;
            }
        }
        cout << sum << endl;
    }

}

C++: #include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <stack>
#include <functional>
#include <queue>
#include <cmath>
#include <set>
#include <map>

#define rep(i,j,k) for(int i=(int)j;i<(int)k;i++)
#define Sort(x) sort((x).begin(),(x).end())
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define vi vector<int>
#define INF (int)1e9
#define INFL 1e18
#define MOD 1e9+7
#define pb push_back
#define MP make_pair
typedef long long int ll;
typedef std::pair<int,int> P;
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

using namespace std;
int main() {
    int n,m;
    while(cin>>n>>m){
        if(n==0&&m==0)return 0;
        vector<P> v(n);
        rep(i,0,n){
            cin>>v[i].fi>>v[i].se;
        }
        Sort(v);
        int ans=0;
        rep(i,0,n){
            while(v[i].fi==v[i+1].fi)i++;
            ans+=v[i].se;
        }
        cout<<ans<<endl;
    }
    
    return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<string>
#include<vector>
#include<map>

using namespace std;

int main(){
	int N,M;
	int dt,vt;
	while(scanf("%d %d",&N,&M)){
		if(N==0&&M==0)
		break;
		map<int, int> mp;
		for(int i=0;i<N;i++){
			scanf("%d %d",&dt,&vt);
			auto itr=mp.find(dt);
			if(itr!=mp.end()){
				if(itr->second < vt)
				mp[dt]=vt;
			}
			else{
				mp[dt]=vt;
			}
		}
		int sum=0;
		for(auto itr=mp.begin();itr!=mp.end();itr++){
			sum+=itr->second;
		}
		printf("%d\n",sum);
	}
}

C++: #include <bits/stdc++.h>
#define int long long
using namespace std;

int N, M;

signed main(){
  
  while(1){
  
    cin>>N>>M;
    if( !N && !M ) break;
    
    int maxv[105] = {};
    
    for(int i=0;i<N;i++){
      int d, v;
      cin>>d>>v;
      maxv[d] = max( maxv[d], v );
    }
    
    int ans = 0;
    
    for(int i=1;i<=M;i++) ans += maxv[i];
    
    cout<<ans<<endl;
    
  }
  
  return 0;
}

C++: #include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<P,int> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-11;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};
const int DX[8]={-1,0,1,0,-1,-1,1,1},DY[8]={0,-1,0,1,-1,1,-1,1};


int main(){;
	while(1){
		int n,m;
		cin>>n>>m;
		if(n==0) break;
		vi a(m);
		for(int i=0;i<n;i++){
			int x,y;
			cin>>x>>y;
			x--;
			a[x]=max(a[x],y);
		}
		int res=0;
		for(auto i:a) res+=i;
		cout<<res<<endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;

#define INF_LL (int64)1e18
#define INF (int32)1e9
#define REP(i, n) for(int64 i = 0;i < (n);i++)
#define FOR(i, a, b) for(int64 i = (a);i < (b);i++)
#define all(x) x.begin(),x.end()
#define fs first
#define sc second

using int32 = int_fast32_t;
using uint32 = uint_fast32_t;
using int64 = int_fast64_t;
using uint64 = uint_fast64_t;
using PII = pair<int32, int32>;
using PLL = pair<int64, int64>;

const double eps = 1e-10;

template<typename A, typename B>inline void chmin(A &a, B b){if(a > b) a = b;}
template<typename A, typename B>inline void chmax(A &a, B b){if(a < b) a = b;}

template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value!=0>::type
fill_v(U &u,const V... v){u=U(v...);}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value==0>::type
fill_v(U &u,const V... v){
  for(auto &e:u) fill_v<T>(e,v...);
}

int main(void) {
	int64 N, M;
	while (cin >> N >> M && N+M) {
		auto pro = make_v<int64>(M, 0);
		REP(i, N) {
			int64 d, v;
			cin >> d >> v; d--;
			pro[d].push_back(v);
		}
		int64 res = 0;
		REP(i, M) {
			sort(all(pro[d]));
			res += pro[d].back();
		}
		cout << res << endl;
	}
}