#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

int main(){
    int n,m;
    while(cin >>n >>m,n){
        vector<int> a(m);
        rep(i,n){
            int d,v;
            cin >>d >>v;
            --d;
            a[d] = max(a[d], v);
        }

        int ans = 0;
        rep(i,m) ans += a[i];
        cout << ans << endl;
    }
    return 0;
}

