#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}

void radix_sort_aux(unsigned*a,unsigned*b,int n){
	int c[256];
	for(int i=0;i<256;++i){
		c[i]=0;
	}
	for(int i=0;i<n;++i){
		++c[a[i]&255];
	}
	int t=0;
	for(int i=256;i--;){
		int u=c[i];
		c[i]=t;
		t+=u;
	}
	for(int i=0;i<n;++i){
		b[c[a[i]&255]++]=a[i]>>8|a[i]<<24;
	}
}

void radix_sort(unsigned*a,int n){
	radix_sort_aux(a,a+n,n);
	radix_sort_aux(a+n,a,n);
	radix_sort_aux(a,a+n,n);
	radix_sort_aux(a+n,a,n);
}

a[200000];

main(){
	char*rp=mmap(0l,1l<<28,1,2,0,0ll);
	RD(n);
	RD(m);
	RD(y);
	--n;
	for(int i=0;i<n;++i){
		RD(t);
		a[i]=t;
	}
	radix_sort(a,n);
	int b=(1<<31)-1;
	{
		int k=m*2;
		for(int i=0;i<m;++i){
			int c=a[i]+a[--k];
			if(b>c){
				b=c;
			}
		}
	}
	int j=m*2;
	if(j>=n){
		j=n-1;
		goto owari;
	}
	if(y+a[j]<b){
		int k=0;
		while(j>0){
			int c=a[j--]+a[k++];
			k+=j==k;
			if(b>c){
				b=c;
			}
			if(y+a[j]>=b){
				goto owari;
			}
		}
		if(y+a[j]<b){
			j=-1;
		}
	}else{
		while(j+1<n&&y+a[j+1]>=b){
			j=j+1;
		}
	}
	owari:;
	printf("%d",j<0?j:a[j]);
}