CUPLAJ_MAXIM_EXEMPLU

#include <cstdio>
#include <vector>
#include <cstring>
#define N 50001
#define FOR(i,a,b) for(int i=(int)(a);i<=(int)(b);++i)
#define FORI(i,V) for(vector <int>::iterator i=(V).begin();i!=(V).end();++i)
using namespace std;
const char iname[]="falkland.in";
const char oname[]="falkland.out";
vector <int> G[N];
int l[N],r[N],u[N];

int pairup(const int n)
{
    if(u[n])
        return 0;
    u[n]=1;
    FORI(i,G[n])
        if(!r[*i])
        {
            l[n]=*i;
            r[*i]=n;
            return 1;
        }
    FORI(i,G[n])
        if (pairup(r[*i]))
        {
            l[n]=*i;
            r[*i]=n;
            return 1;
        }
    return 0;
}

int main(void)
{
    freopen(iname,"r",stdin);
    int n,m,k;
    scanf("%d %d %d",&n,&m,&k);
    int x,y;
    while(k--)
        scanf("%d %d",&x,&y),G[x].push_back(y);
    for(int change=1;change;)
    {
        change=0;
        memset(u,0,sizeof(u));
        FOR (i,1,n)
            if(!l[i])
                change|=pairup(i);
    }
    int r=0;
    FOR(i,1,n)
		r+=(l[i]>0);
    freopen(oname,"w",stdout);
    printf("%d\n",r);
    FOR(i,1,n)
        if(l[i]>0)
            printf("%d %d\n",i,l[i]);
    return 0;
}