#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N=1e5+10;
LL l[N], r[N]; int m, n; LL F; 
struct node{LL s, q;} a[N];
bool cmp(node n1, node n2){
	return n1.s < n2.s;
}
void work(){
	sort(a+1, a+n+1, cmp);
	int t=m/2; LL sum=0;
	priority_queue<LL> Q1;
	for(int i=1; i<=n; i++){
		if(i<=t){
            Q1.push(a[i].q);
            sum += a[i].q;
            continue;
        }
        l[i] = sum;
        if(a[i].q < Q1.top()){
            sum -= Q1.top();
            Q1.pop();
            Q1.push(a[i].q);
            sum += a[i].q;
        }
	}
	sum=0;
	priority_queue<LL> Q2;
	for(int i=n; i>=1; i--){
		if(i > n-t){
            Q2.push(a[i].q);
            sum += a[i].q;
            continue;
        }
        r[i] = sum;
        if(a[i].q < Q2.top()){
            sum -= Q2.top();
            Q2.pop();
            Q2.push(a[i].q);
            sum += a[i].q;
        }
	}
	for(int i=n-t; i > t; i--){
		if(l[i] + a[i].q + r[i] <= F){
			printf("%lld\n", a[i].s);
			return ;
		}
	}
	printf("-1\n");
	return ;
}
int main(){
	scanf("%d%d%lld", &m, &n, &F);
	for(int i=1; i<=n; i++) scanf("%lld%lld", &a[i].s, &a[i].q);
	work();
	return 0;
}

by hansang:

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N=1e5+10;
LL l[N], r[N]; int m, n; LL F;
struct node{LL s, q;} a[N];
bool cmp(node n1, node n2){
return n1.s<n2.s;
}
void work(){
sort(a+1, a+n+1, cmp);
int t=m/2; LL sum=0;
priority_queue<LL> Q1;
for(int i=1; i<=n; i++){
if(i<=t){
Q1.push(a[i].q);
sum+=a[i].q;
continue;
}
l[i]=sum;
if(a[i].q<Q1.top()){
sum-=Q1.top();
Q1.pop();
Q1.push(a[i].q);
sum+=a[i].q;
}
}
sum=0;
priority_queue<LL> Q2;
for(int i=n; i>=1; i--){
if(i>n-t){
Q2.push(a[i].q);
sum+=a[i].q;
continue;
}
r[i]=sum;
if(a[i].q<Q2.top()){
sum-=Q2.top();
Q2.pop();
Q2.push(a[i].q);
sum+=a[i].q;
}
}
for(int i=n-t; i>t; i--){
if(l[i]+a[i].q+r[i]<=F){
printf("%lld\n", a[i].s);
return ;
}
}
printf("-1\n");
return ;
}
int main(){
scanf("%d%d%lld", &m, &n, &F);
for(int i=1; i<=n; i++) scanf("%lld%lld", &a[i].s, &a[i].q);
work();
return 0;
}