甚至连O2都不用开，卡卡常就行。

#include <cstdlib>
#include <cstdio>
inline int read()
{
    register int r(0);register char c(getchar());
    while(c < '0' || c > '9') c = getchar();
    while(c >= '0' && c <= '9') r = r * 10 + c - '0', c = getchar();
    return r;
}
inline int out(int x)
{
    if(x >= 10) out(x / 10);
    putchar(x % 10 + '0');
}
inline int comp(const void *a,const void *b)
{
    return *(int*)a - *(int*)b;
}
int main()
{
    register int a[5000001], n(read()), k(read());
	for(register int i(0);i < n;++i)
		a[i] = read();
	qsort(a, n, 4, comp);
	out(a[k]);
	return 0;	
}

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