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 <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <stack>
#include <functional>
#include <queue>
#include <cmath>
#include <set>
#include <map>
#include <numeric>

#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 1000000007
#define pb push_back
#define MP make_pair
typedef long long int ll;
typedef std::pair<int,int> P;
int D=1;
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

using namespace std;

int main(){
    while(1){
        int n,m;
        cin>>n>>m;
        if(n==0&&m==0)break;
        vector<int> ans(n,0);
        rep(i,0,n){
            int d,v;
            cin>>d>>v;
            ans[d-1]=max(ans[d-1],v);
        }
        
        cout<<accumulate(ans.begin(),ans.begin()+m,0)<<endl;
    }
    
    
    return 0;
}

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

#define EPS (1e-7)
#define INF (1e9)
#define LLINF (1e18)
#define PI (acos(-1))
#define MOD (1000000007)
#define ALL(v) (v).begin(), (v).end()
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

//-------------------------------------

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    while (true)
    {
        int n, m;
        cin >> n >> m;
        if (n == 0 && m == 0)
        {
            break;
        }
        vector<int> q[m + 1];
        for (int i = 0; i < n; i++)
        {
            int d, v;
            cin >> d >> v;
            q[d].push_back(v);
        }
        int ans = 0;
        for (int i = 1; i <= m; i++)
        {
            sort(q[i].rbegin(), q[i].rend());
            ans += q[i][0];
        }
        cout << ans << endl;
    }
}

C++: #include <stdio.h>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
typedef long long int ll;
#define BIG_NUM 2000000000
#define MOD 1000000007
using namespace std;

int main(){

	int N,M,table[101],ans,d,v;

	while(true){
		scanf("%d %d",&N,&M);
		if(N == 0 && M == 0)break;

		for(int i = 1; i <= M; i++)table[i] = 0;

		ans = 0;

		for(int i = 0; i < N; i++){
			scanf("%d %d",&d,&v);
			table[d] = max(table[d],v);
		}

		for(int i = 1; i <= M; i++)ans += table[i];

		printf("%d\n",ans);
	}

   return 0;
}

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

typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
typedef pair<ll, pair<ll, ll> > P3;

const ll MOD = ll(1e9 + 7);
const ll LLINF = LLONG_MAX;
const int IINF = INT_MAX;
const int MAX_N = int(1e5) + 5;
const double EPS = 1e-8;
int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};

#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++)

int main() {
    while(1){
        int n,m;
        cin >> n >> m;
        if(n==0)break;
        int a[105]{},res = 0;
        REP(i,n){
            int d,v;
            cin >> d >> v;
            a[d] = max(a[d],v);
        } 
        FOR(i,1,m+1){
            res += a[i];
        }
        cout << res << endl;
    }
    return 0;
}