C :

#include <stdio.h>
#include <stdlib.h>

typedef struct _Link
{
    int Id;
    int Score;
    struct _Link * Prev;
    struct _Link * Next;
}Link,*PLink;

void input(PLink * nml,int nm)
{
    int i=0;
    for(;i<nm;++i)
    {
        PLink l =(PLink)malloc(sizeof(Link));
        if(*nml)
        {
            (*nml)->Next = l; 
            l->Prev = (*nml);
            l->Next = NULL;
            (*nml)=  (*nml)->Next ;
        }
        else
        {
            (*nml) = l;
            l->Prev=NULL;
            l->Next = NULL;
        }
        scanf("%d %d",&((*nml)->Id),&((*nml)->Score));
    }
}

PLink merge(PLink* nl,PLink* ml,int n,int m)
{
    PLink l = n<m? *nl:*ml;
    while((*nl)->Prev)*nl=(*nl)->Prev;
    while((*ml)->Prev)*ml=(*ml)->Prev;
    if(n<m)
    {
        l->Next= *ml;
        (*ml)->Prev = l;
        return *nl;
    }
    l->Next = *nl;
    (*nl)->Prev = l;
    return *ml;
}

void sort(PLink  h)
{
    PLink i,j;
    for(i=h;i->Next;i=i->Next)
    {
        for(j=i->Next;(j)&&(j->Prev);j=j->Prev)
        {
            if(j->Id<(j->Prev->Id))
            {
                //change values
                j->Id +=j->Prev->Id;
                j->Prev->Id = j->Id-(j->Prev->Id);
                j->Id-=j->Prev->Id;
                j->Score +=j->Prev->Score;
                j->Prev->Score = j->Score-(j->Prev->Score);
                j->Score-=j->Prev->Score;
            }
        }
    }
}

int main()
{
    int N,M,ni,mi;
    PLink NL=0,ML=0,HL=0;
    scanf("%d %d",&N,&M);
    //input
    input(&NL,N);
    input(&ML,M);
    //merge
    HL = merge(&NL,&ML,N,M);
    //sort
    sort(HL);
    //output
    while(HL)
    {
        printf("%d %d\n",HL->Id,HL->Score);
        HL = HL->Next;
    }
    return 0;
}

C++ :

#include<bits/stdc++.h>
using namespace std;
struct f
{
    int a,b;
}a[100000];
bool cmp(f a,f b)
{
    return a.a<b.a;
}
int n,m;
int main()
{
    cin>>n>>m;
    for(int i=1;i<=n+m;i++)
    cin>>a[i].a>>a[i].b;
    sort(a+1,a+n+m+1,cmp);
    for(int i=1;i<=n+m;i++)
    cout<<a[i].a<<" "<<a[i].b<<"\n";
    return 0;
}