#include<bits/stdc++.h>
#define N 100010
#define For(i,a,b) for(register int i=a;i<=b;i++)
using namespace std;
int L,R,m,vis[N],ml[N],mr[N],ans;
vector<int> go[N];
inline bool dfs(int x,int t)
{
    if(vis[x] == t) return false;
    vis[x]=t;
    for(int to:go[x])
        if(!mr[to] || dfs(mr[to],t))
            {ml[x]=to,mr[to]=x;return true;}
    return false;
}

int main()
{
    ios::sync_with_stdio(false);
    cin>>L>>R>>m;
    For(i,1,m) 
    {
        int x,y;cin>>x>>y;
        go[x+1].push_back(y+1);
    }For(i,1,L) ans+=dfs(i,i);
    cout<<ans<<'\n';
    For(i,1,L) if(ml[i]) cout<<i-1<<' '<<ml[i]-1<<'\n';
    return 0;
}