#include<iostream> #include<cstdio> #include<cstring> #include<string> #include<algorithm> using namespace std; const int maxn=100007; const double eps=1e-10; int n,m; int h[maxn]; double left=0.0,right=10000000.0,mid; void judge{ double sum=h[0]+2*mid; int cnt=1; for(int i=1;i<n;i++){ if(sum<h[i]){ sum=h[i]+2*mid; cnt++; } } if(cnt>m) left=mid; else right=mid; } int main() { while(~scanf()) scanf("%d%d",&m,&n); for(int i=0;i<n;i++){ scanf("%d",&h[i]); } sort(h,h+n); while(right-left>=eps){ judge(mid); } printf("%.1f ",mid); }