#include<bits/stdc++.h>
using namespace std;
const int N = 2000003;
template<typename T>
bool chmin(T &a, const T &b){if(a > b) return a = b, 1; return 0;}
int n1, n2, m, pr[N], qr[N], U[N], hd[N], cur[N], to[N], nxt[N];
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int mt1[N], mt2[N], mt[N], dp1[N], dp2[N], q[N], fr, re, ans;
bool vis[N];
bool bfs(){
	memset(dp1, 0x3f, (n1 + 1) << 2);
	memset(dp2, 0x3f, (n2 + 1) << 2);
	memset(vis, 0, n2 + 1);
	memcpy(cur, hd, (n1 + 1) << 2);
	fr = re = 0;
	for(int i = 1;i <= n1;++ i) if(!mt1[i]) dp1[q[re ++] = i] = 0;
	int mn = 1e9;
	while(fr < re){
		int u = q[fr ++];
		if(dp1[u] >= mn) break;
		for(int i = hd[u];i;i = nxt[i]){
			int v = to[i];
			if(chmin(dp2[v], dp1[u] + 1)){
				if(mt2[v]) dp1[q[re ++] = mt2[v]] = dp2[v] + 1;
				else chmin(mn, dp2[v]);
			}
		}
	}
	return mn < 1e9;
}
bool dfs(int u){
	for(int &i = cur[u];i;i = nxt[i]){
		int v = to[i];
		if(!vis[v] && dp2[v] == dp1[u] + 1){
			vis[v] = true;
			if(!mt2[v] || dfs(mt2[v])){
				mt1[mt2[v] = u] = v;
				mt[u] = i;
				return true;
			}
		}
	}
	return false;
}
int main(){
	clock_t st = clock();
	ios::sync_with_stdio(0);
	cin >> n1 >> n2 >> m;
	iota(pr, pr + m + 1, 0);
	shuffle(pr + 1, pr + m + 1, rng);
	for(int i = 1;i <= m;++ i){cin >> U[pr[i]] >> to[pr[i]]; qr[pr[i]] = i;}
	for(int i = 1;i <= m;++ i){nxt[i] = hd[U[i]]; hd[U[i]] = i;}
	for(int $ = 0;$ < 19 && clock() - st < 3.5 * CLOCKS_PER_SEC && bfs();++ $)
		for(int i = 1;i <= n1;++ i) if(!mt1[i] && dfs(i)) ++ ans;
	printf("%d\n", ans);
	for(int i = 1;i <= n1;++ i) if(mt[i]) printf("%d\n", qr[mt[i]]);
}