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#include<iostream>
#include<list>
#include<stdio.h>
#include<map>
#include<set>
#include<vector>
using namespace std;
#define ull unsigned long long int
#define FOR(i,n) for(int i=0;i<(n);++i)
#define FORI(i,start,n) for(int i=(start);i<(n);++i)
#define FORit(it,collection) for(auto it = collection.cbegin(); it != collection.cend(); it++)
#define SKIP -5000
#define znakow 26
#define DEBUG 0
#define dcout DEBUG && cout
int inline min(int a,int b){return a>b?b:a;}
int inline max(int a,int b){return a<b?b:a;}
class N{
	public:
		vector<int> incomming;
		vector<int> outgoing;
		vector<int> connections;
		N(){
		}
		void addOutgoing(int toNode){
			outgoing.push_back(toNode);
		}
		void addIncomming(int fromNode){
			incomming.push_back(fromNode);
		}
};
class Paths{
	public:
		N*nodes;
		int*t;
		int v;
		Paths(N*nodes,int v){
			this->nodes=nodes;
			this->v=v;
			t=new int[v];
			FOR(i,v){
				int maxPath=1;
				FORit(it, nodes[i].incomming){
					maxPath=max(t[*it] + 1, maxPath);
				}
				t[i]=maxPath;
			}
			//FOR(i,v)dcout<<t[i]<<' ';dcout<<endl;
		}
		int findMaxNode() {
			int mxv=-1;
			int mxi=-1;
			FOR(i,v){
				//dcout<<t[i]<<' ';
				if(mxv<t[i]) {
					mxv=t[i];
					mxi=i;
				}	
			}
			//dcout<<"found max node "<<mxi<<" with value "<<mxv<<endl;
			return mxi;
		}
		int remove(int node){
			int oldT=t[node];
			t[node]=SKIP;
			FORit(it, nodes[node].outgoing){
				incommingRemoved(*it, oldT);
			}
			return oldT;
		}
		void incommingRemoved(int node, int oldIncommingValue){
			if(t[node]==SKIP)return;
			int myOldT = t[node];
			if(t[node]==oldIncommingValue+1){
				int maxPath=1;
				FORit(it, nodes[node].incomming){
					maxPath=max(t[*it] + 1, maxPath);
				}
				t[node]=maxPath;
				if(myOldT!=t[node]){
					FORit(it, nodes[node].outgoing){
						incommingRemoved(*it, myOldT);
					}
				}
			}
		}
		void incommingAdded(int node, int newIncommingValue){
			if(t[node]==SKIP)return;
			if(t[node]<newIncommingValue+1){
				t[node]=newIncommingValue+1;
				FORit(it, nodes[node].outgoing){
					incommingAdded(*it, t[node]);
				}
			}
		}
		void restore(int node, int newT){
			//dcout<<"before restore \n";
			//print();
			t[node]=newT;
			FORit(it, nodes[node].outgoing){
				incommingAdded(*it, newT);
			}
			//dcout<<"after restore  \n";
			//print();
		}
		int getNodePath(int node){
			return t[node];
		}
		int getPrevios(int node){
			if(t[node]==SKIP){cout<<"current is removed"<<endl;}
			FORit(it, nodes[node].incomming){
				if(t[*it]+1==t[node]){
					//dcout<<"Node "<<*it<<" is preceding "<<node<<endl;
					return *it;
				}
			}
			return -1;
		}
		void print(){
			//FOR(i,v)dcout<<t[i]<<' ';dcout<<endl;
		}
};
int removeVertices(int toRemove, Paths*paths){

	int current = paths->findMaxNode();
	if(current==-1){
		return 9999;
		//dcout<<"max node is -1"<<endl;
	}
	int currentDepth = paths->getNodePath(current);
	if(toRemove==0)return currentDepth;

	int minimumDepth=currentDepth;

	do{
		int oldPath = paths->remove(current);

		minimumDepth=min(minimumDepth, removeVertices(toRemove-1, paths));
		//dcout<<"minimumDepth is "<<minimumDepth<<endl;

		paths->restore(current, oldPath);

		current = paths->getPrevios(current);paths->print();

	} while(current!=-1);

	return minimumDepth;
}
int main(){
    ios::sync_with_stdio(false);
	int v,e,r;
	cin>>v>>e>>r;
	if(v<=r){
		cout<<"0"<<endl;
		return 0;
	}
	if(e<=r || v+1==r){
		cout<<"1"<<endl;
		return 0;	
	}
	N*nodes=new N[v];
	FOR(i,e){
		int a,b;
		cin>>a>>b;
		--a;
		--b;
		nodes[a].addOutgoing(b);
		nodes[b].addIncomming(a);
	}
	Paths*paths = new Paths(nodes,v);
	cout<<removeVertices(r, paths)<<endl;
    return 0;
}