#include <bits/stdc++.h>
#define FastIo() ios_base::sync_with_stdio(false), cin.tie(nullptr),cout.tie(nullptr);
using namespace  std;
const int nmax = 10005;

vector<int> G[nmax+1];
vector<int> used;
vector<int> mt;

int n,m,e;
int x,y;
int nr;

bool try_kuhn(int x){
    if(used[x]) return false;
    used[x]=true;
    for(int y:G[x]){
        if(mt[y]==-1 || try_kuhn(mt[y])){
            mt[y]=x;
            return true;
        }
    }
    return false;
}
int main(){
    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);
    FastIo()
    cin>>n>>m>>e;
    for(int i=1;i<=e;i++){
        cin>>x>>y;
        G[x].push_back(y);
    }

    bitset<nmax> used1;
    mt.assign(m+1,-1);

    for(int x=1;x<=n;x++){
        for(int y:G[x]){
            if(mt[y]==-1){
                used1[y]=true;
                mt[y]=x;
                nr++;
                break;
            }
        }
    }

    for(int x=1;x<=n;x++){
        if(used1[x]) continue;
        used.assign(n+1,false);
        if(try_kuhn(x)) nr++;
    }
    cout<<nr<<'\n';
    for(int i=1;i<=m;i++){
        if(mt[i]!=-1)
            cout<<mt[i]<<' '<<i<<'\n';
    }

}