#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>

#define int long long
#define PR pair<int,int>

using namespace std;

const int kN=5e5+5;

struct Smt{
	int s[2],siz,sum;
	#define Son(p,k) tree[p].s[k]
	#define Sum(p) tree[p].sum
	#define Siz(p) tree[p].siz
}tree[kN<<5];

struct Node{
	int a,b;
}q[kN];

int n,c,rt[kN],len,cnt,b[kN],f;

bool cmp(Node x,Node y){
	return x.a<y.a;
}

void Build(int l,int r,int &p){
	p=++cnt;
	if(l==r){return;}
	int mid=(l+r)>>1;
	Build(l,mid,Son(p,0));Build(mid+1,r,Son(p,1));
}

void Modify(int l,int r,int k,int p1,int &p2){
	p2=++cnt;
	tree[p2]=tree[p1];
	if(l==r){
		Siz(p2)++;Sum(p2)+=b[k];
		return;
	}
	int mid=(l+r)>>1;
	if(k<=mid){Modify(l,mid,k,Son(p1,0),Son(p2,0));}
	else{Modify(mid+1,r,k,Son(p1,1),Son(p2,1));}
	Siz(p2)=Siz(Son(p2,0))+Siz(Son(p2,1));
	Sum(p2)=Sum(Son(p2,0))+Sum(Son(p2,1));
}

int Query(int l,int r,int k,int p1,int p2){
	if(l==r){return Sum(p2)/Siz(p2)*k;}
	int mid=(l+r)>>1,sum=Siz(Son(p2,0))-Siz(Son(p1,0));
	if(sum>k){return Query(l,mid,k,Son(p1,0),Son(p2,0));}
	else if(sum==k){return Sum(Son(p2,0))-Sum(Son(p1,0));}
	else{return Sum(Son(p2,0))-Sum(Son(p1,0))+Query(mid+1,r,k-sum,Son(p1,1),Son(p2,1));}
}

signed main(){
	scanf("%lld%lld%lld",&n,&c,&f);
	for(int i=1;i<=c;++i){
		scanf("%lld%lld",&q[i].a,&q[i].b);
		b[i]=q[i].b;
	}
	sort(q+1,q+1+c,cmp);
	sort(b+1,b+1+c);
	len=unique(b+1,b+1+c)-(b+1);
	Build(1,len,rt[0]);
	for(int i=1;i<=c;++i){
		int k=lower_bound(b+1,b+1+c,q[i].b)-b;
		Modify(1,len,k,rt[i-1],rt[i]);
	}
	int tmp;n=(n-1)/2;
	for(int i=c-n;i>n;--i){
		tmp=Query(1,len,n,rt[0],rt[i-1])+Query(1,len,n,rt[i],rt[c])+q[i].b;
		if(tmp<=f){
			printf("%lld\n",q[i].a);
			return 0;
		}
	}
	printf("-1\n");
	return 0;
}