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 <algorithm>
#include <math.h>
#include <string.h>
#include <map>
#include <fstream>
#include <string>

using namespace std;

struct mondai {
	int suisen;
	int nanido;
	int number;
};
bool hyouka(mondai a, mondai b) {
	if (a.nanido == b.nanido) {
		return a.suisen >= b.suisen;
	}
	else {
		return a.nanido >= b.nanido;
	}
}


int main() {
	while (true) {
		int n, m;
		cin >> n >> m;
		if (n == 0) {
			break;
		}
		mondai a[1000];
		int d, v;
		for (int i = 0; i < n; i++) {
			cin >> d >> v;
			a[i].suisen = v;
			a[i].nanido = d;
		}
		sort(a, a + n, hyouka);
		int tmpsuisen = 0;
		int tmpnanido = 1;
		int cnt = 0;
		for (int i = 0; i < n; i++) {
		//	cout << "nanido:" << a[i].nanido << "suisen:" << a[i].suisen << endl;
			if (tmpnanido != a[i].nanido) {
			//	cout << "足したよ ; " << tmpsuisen << " " << i << endl;
				tmpnanido = a[i].nanido;
				cnt += tmpsuisen;
				tmpsuisen = 0;
			}
			if (tmpsuisen < a[i].suisen) {
				tmpsuisen = a[i].suisen; 
			}

		}
		cnt += tmpsuisen;
		cout << cnt << endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
/*{{{*/  //template
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
constexpr int INF = numeric_limits<int>::max()/2;
constexpr long long LINF = numeric_limits<long long>::max()/3;
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
//struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double{ double d; explicit Double(double x) : d(x){} };
ostream& operator<<(ostream& os,const Double x){ os << fixed << setprecision(20) << x.d; return os; }
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os, const map<T,U>& mp){ os << "{"; for(auto& p : mp){ os << p << ","; } os << "}"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os,const pair<T,U>& p){ os << "(" << p.first << ","<< p.second <<")"; return os; }
template<typename T> ostream& operator<<(ostream& os,const set<T>& st){ os<<"{"; for(T v:st) os<<v<<","; os <<"}"; return os; }
template<typename T,typename U> inline void chmax(T &x,U y){ if(y>x) x = y; }
template<typename T,typename U> inline void chmin(T &x,U y){ if(y<x) x = y; }
using ll = long long;
using ull = unsigned long long;
using pii = std::pair<int,int>;
using vi = std::vector<int>;
typedef vector<vi> vvi;
ll gcd(ll a,ll b){ if(b==0) return a; else return gcd(b,a%b); }
constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }
//constexpr double eps = 1e-14; 
constexpr double eps = 1e-10; 
constexpr ll mod = 1e9+7;
const int dx[]={1,0,-1,0} ,dy[] = {0,1,0,-1};
/*}}}*/

int n,m;

void solve(){
    vector<int> a(m+1,0);
    rep(i,n){
        int d,v;
        cin >> d >> v;
        d--;
        a[d] = max(a[d],v);
    }
    int ans = accumulate(all(a),0);
    cout << ans << endl;
}

int main(){
    while(cin>>n>>m){
        if(!n and !m) break;
        solve();
    }
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define f(i,x,n) for(int i=x;i<(int)(n);++i)
#define all(x) (x).begin(),(x).end()
const int mod=1000000007,MAX=200005,INF=1<<30;

int main(){
    
    std::ifstream in("text.txt");
    std::cin.rdbuf(in.rdbuf());
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    while(1){
        int N,M;cin>>N>>M;
        if(N+M==0) break;
        
        vector<int> A(M);
        
        for(int i=0;i<N;i++){
            int a,b;cin>>a>>b;
            a--;
            A[a]=max(A[a],b);
        }
        
        int sum=0;
        
        for(int i=0;i<M;i++){
            sum+=A[i];
        }
        
        cout<<sum<<endl;
    }
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <numeric>

using namespace std;

using lint = long long;
using ldouble = long double;

bool solve() {
    int N, M;
    cin >> N >> M;
    if (N == 0) return false;

    vector<int> ma(M, 0);
    for (int i = 0; i < N; ++i) {
        int d, v;
        cin >> d >> v;
        --d;
        ma[d] = max(ma[d], v);
    }
    cout << accumulate(ma.begin(), ma.end(), 0) << endl;
    return true;
}

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