#include <bits/stdc++.h> using namespace std; typedef signed long long ll; #undef _P #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x<(to);x++) #define FORR(x,arr) for(auto& x:arr) #define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++) #define ALL(a) (a.begin()),(a.end()) #define ZERO(a) memset(a,0,sizeof(a)) #define MINUS(a) memset(a,0xff,sizeof(a)) //------------------------------------------------------- int N,M,D[10101]; void solve() { int i,j,k,l,r,x,y; string s; cin>>N>>M; FOR(i,M) cin>>D[i]; sort(D,D+M); int mi=1<<30; for(x=0;x<M;x++) { y=x+(N-1); if(y>=M) continue; if(D[x]>=0) mi=min(mi,D[y]); if(D[y]<=0) mi=min(mi,-D[x]); if(D[x]<=0 && D[y]>=0) { mi=min(mi,-D[x]+2*D[y]); mi=min(mi,-2*D[x]+D[y]); } } cout<<mi<<endl; } int main(int argc,char** argv){ string s;int i; if(argc==1) ios::sync_with_stdio(false), cin.tie(0); FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin); solve(); return 0; }