#include<fstream>
#include<cstring>
#include<vector>
using namespace std;
ifstream in("cuplaj.in");
ofstream out("cuplaj.out");
const int Nmax = 10001;
vector<int> G[Nmax];
int N,M,A[Nmax],B[Nmax],mark[Nmax];
int addpath(int x){
    if(mark[x]) return 0;
    mark[x]=1;
    for(vector<int>::iterator it=G[x].begin();it!=G[x].end();++it){
        if(!B[*it] || addpath(B[*it])){
            A[x]=*it;
            B[*it]=x;
            return 1;
        }
    }
    return 0;
}
int main(){
    int edges;
    in>>N>>M>>edges;
    for(;edges;--edges){
        int x,y;
        in>>x>>y;
        G[x].push_back(y);
    }
    int p=1,mf=0;
    while(p){
        p=0;
        memset(mark,0,sizeof(mark));
        for(int i=1;i<=N;i++) if(!A[i]) p|=addpath(i);
    }
    for(int i=1;i<=N;i++) if(A[i]) mf++;
    out<<mf<<'\n';
    for(int i=1;i<=N;i++) if(A[i]) out<<i<<' '<<A[i]<<'\n';
    return 0;
}