s=require("fs").readFileSync("/dev/stdin","utf8");

A = s.split('\n')
B = A[0].split(' ')[0] | 0
C = A[0].split(' ')[1] | 0

// a = [...Array(B)].map((_, i) => A[i + 1] | 0)
a = []
for (i = 0; i < B; i++) {
	a.push(A[i + 1] | 0)
}

a.sort((a,b) =>a < b ? -1 : 1)

l = C - 1
// b = [...Array(a.length - l)].map((_, i) => a[i + l] - a[i])
b = []
for (i = 0; i < a.length - l; i++) {
	b.push(a[i + l] - a[i])
}

console.log(Math.min(...b))
