#include <bits/stdc++.h>

int calc(int left, int right) {
  if( left * right >= 0 ) return std::max(std::abs(left), std::abs(right));
  int nl = std::abs(left);
  int nr = std::abs(right);
  return std::min(nl, nr) * 2 + std::max(nl, nr);
}

int main() {
  int n; scanf("%d", &n);
  int m; scanf("%d", &m);
  int xs[1024];
  for(int i = 0; i < m; ++i) {
    scanf("%d", &xs[i]);
  }
  std::sort(xs, xs + m);

  int res = (1 << 28);
  for(int i = 0; i + n - 1 < m; ++i) {
    res = std::min(res, calc(xs[i], xs[i + n - 1]));
  }
  printf("%d\n", res);
    
  return 0;
}