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#include <iostream>
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>
#include <string>
#include <bitset>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <algorithm>
#include <sstream>
#include <stack>
#include <iomanip>
using namespace std;
#define pb push_back
#define mp make_pair
typedef pair<int,int> pii;
typedef long long ll;
typedef double ld;
typedef vector<int> vi;
#define fi first
#define se second
#define fe first
#define FO(x) {freopen(#x".in","r",stdin);freopen(#x".out","w",stdout);}
#define Edg int M=0,fst[SZ],vb[SZ],nxt[SZ];void ad_de(int a,int b){++M;nxt[M]=fst[a];fst[a]=M;vb[M]=b;}void adde(int a,int b){ad_de(a,b);ad_de(b,a);}
#define Edgc int M=0,fst[SZ],vb[SZ],nxt[SZ],vc[SZ];void ad_de(int a,int b,int c){++M;nxt[M]=fst[a];fst[a]=M;vb[M]=b;vc[M]=c;}void adde(int a,int b,int c){ad_de(a,b,c);ad_de(b,a,c);}
#define es(x,e) (int e=fst[x];e;e=nxt[e])
#define esb(x,e,b) (int e=fst[x],b=vb[e];e;e=nxt[e],b=vb[e])
#define SZ 666666
int n,m,k,ans=1e9,aa[SZ],A[SZ],B[SZ];
pii as[SZ];
vector<vector<int> > cur;
vector<pii> vs[2333];
int rs[SZ],ff[SZ];
vector<int> s[2333];
int gf(int x) {return (ff[x]<0)?x:(ff[x]=gf(ff[x]));}
void dfs(const vector<vector<int> >& v,int g)
{
	if(!v.size())
	{
		ans=0; return;
	}
	if(!g)
	{
		int ca=0;
		for(int i=int(v.size())-1;i>=0;--i)
		{
			aa[i]=1;
			for(auto g:v[i])
				aa[i]=max(aa[i],aa[g]+1);
			ca=max(ca,aa[i]);
			if(ca>=ans) return;
		}
		ans=ca; return;
	}
	if(g==1)
	{
		for(int i=0;i<v.size();++i) s[i].clear();
		for(int i=0;i<v.size();++i)
			for(auto t:v[i]) s[t].pb(i);
		for(int i=int(v.size())-1;i>=0;--i)
		{
			A[i]=1;
			for(auto g:v[i])
				A[i]=max(A[i],A[g]+1);			
		}
		for(int i=0;i<=int(v.size());++i) ff[i]=-1;
		for(int i=0;i<int(v.size());++i)
		{
			B[i]=1;
			for(auto g:s[i])
				B[i]=max(B[i],B[g]+1);
		}
		for(int j=1;j<=int(v.size());++j) vs[j].clear();
		vs[0].pb(mp(0,int(v.size())-1));
		for(int i=0;i<int(v.size());++i)
			vs[A[i]].pb(mp(0,i-1)),
			vs[B[i]].pb(mp(i+1,int(v.size())-1));
		for(int i=0;i<int(v.size());++i)
			for(auto g:v[i])
				if(i+1<g)
					vs[A[g]+B[i]].pb(mp(i+1,g-1));
		for(int i=int(v.size());i>=0;--i)
			for(auto t:vs[i])
				for(int x=gf(t.fi);x<=t.se;)
					rs[x]=i,ff[x]=gf(x+1),x=ff[x];
		for(int i=0;i<int(v.size());++i)
			ans=min(ans,rs[i]);
		return;
	}
	pii ca(0,0);
	for(int i=int(v.size())-1;i>=0;--i)
	{
		as[i]=pii(1,-1);
		for(auto g:v[i])
			as[i]=max(as[i],pii(as[g].fi+1,g));
		ca=max(ca,pii(as[i].fi,i));
	}
	int x=ca.se;
	vector<int> vv;
	while(x>=0)
		vv.pb(x),x=as[x].se;
	for(auto t:vv)
	{
		vector<vector<int> > s(v.size()-1);
		for(int i=0;i<v.size();++i)
		{
			if(i==t) continue;
			for(auto g:v[i])
				if(g>t) s[i-(i>t)].pb(g-1);
				else if(g<t) s[i-(i>t)].pb(g);
		}
		dfs(s,g-1);
	}
}
int main()
{
	cin>>n>>m>>k;
	if(k>=n)
	{
		puts("0");
		return 0;
	}
	cur.resize(n);
	set<pii> ts;
	for(int i=1,a,b;i<=m;++i)
		cin>>a>>b,ts.insert(pii(a,b));
	for(auto s:ts)
		cur[s.fi-1].pb(s.se-1);
	dfs(cur,k); cout<<ans<<"\n";
}