C++ :

/*
	author :hzoi_ztx
	title  :奖学金 
	ALG    :二分 
	comment:

	[2014 10 15 test]
*/

#include <cstdio>
#include <algorithm>
#include <queue>

#define  maxn  10002
#define  maxc  100002

struct pig{
	long long a , b , p ;
} a[maxc] ;

long long n , c ;
long long mid = 0 ;
long long F ;
long long s1 = 0 , s2 = 0 ;
long long cc[maxc] = {0} ;
bool L[maxc] = {0} ;//记录的都是值排序后的位置 
bool R[maxc] = {0} ;

bool cmp1(const pig a , const pig b) {
	return a.b < b.b ;
}

bool cmp2(const pig a , const pig b) {
	return a.a > b.a ;
}

std::priority_queue<long long>q1,q2 ;//大根 

int main() {
	//#define READ
	#ifdef  READ
		freopen("finace.in" ,"r",stdin ) ;
		freopen("finace.out","w",stdout) ;
	#endif
	long long i , j ;
	scanf("%lld%lld%lld", &n , &c , &F ) ;
	for (i = 1 ; i <= c ; i ++ )
		scanf("%lld%lld", &a[i].a , &a[i].b ) ;
	std::sort(a+1 , a+c+1 , cmp1) ;
	for (i = 1 ; i <= c ; i ++ ) a[i].p = i , cc[i] = a[i].b ;
	std::sort(a+1 , a+c+1 , cmp2) ;
	mid = (n>>1)+1 ;
	for (i = 1 ; i < mid ; i ++ ) {
		s1 += a[i].b ; q1.push(a[i].p) ;
		L[a[i].p] = true ;
	}
	L[mid] = true ;
	j = 0 ;
	for (i = 1 ; i <= c ; i ++ ) {
		if (L[i]) continue ;
		//printf("%d\n",i);
		q2.push(-i) ;
		if (++j <= mid-1) {s2 += cc[i] ; R[i] = true ;}
	}
	//printf("%lld %lld %d\n",s1,s2,a[mid].b) ;
	if (s1+s2+a[mid].b <= F) {
		printf("%lld\n",a[mid].a) ;
		return 0 ;
	}
	long long now ;
	for (i = mid+1 ; i+mid-1 <= c ; i ++ ) {
		L[a[i].p] = true ;
		if (a[i-1].p < q1.top()) {//维护左边 
			s1 -= cc[q1.top()] ;
			s1 += cc[a[i-1].p] ;
			q1.pop() ;
			q1.push(a[i-1].p) ;
		}
		
		if (R[a[i].p]) {//维护右边 
			s2 -= a[i].b ;
			R[a[i].p] = false ;
			while (!q2.empty() && L[-q2.top()]) {
				q2.pop() ;
			}
			s2 += cc[-q2.top()] ;
			R[-q2.top()] = true ;
		}
		
		if (s1+s2+a[i].b <= F) {
			printf("%lld\n", a[i].a ) ;
			return 0 ;
		}
	}
	printf("-1\n") ;
	return 0 ;
}