#include<cstdio>#include<iostream>#include<algorithm>#include<cstring>#include<cmath>#include<vector>#include<queue>#include<map>#include<set>#include<stack>#include<cstdlib>#define INF 100000000#define fi first#define se secondusing namespace std;typedef long long LL;typedef pair<int,int> pii;struct Edge{ int from,to; double d; int pre;}e[40005];int h[10005]={0},cou=0;void Addedge(int from,int to,double ds){ cou++; e[cou]=((Edge){from,to,ds,h[from]}); h[from]=cou;}int n,m;inline int bh(int i,int j){ return (i-1)*m+j;}int hi[10005],inq[10005];double dis[10005];int main(){ double v0,v; int i,j,x,u; cin>>v0>>n>>m; for(i=1;i<=n;i++) for(j=1;j<=m;j++) { x=bh(i,j); //printf("i=%d j=%dn",i,j); //cout<<x<<endl; scanf("%d",&hi[x]); v=pow(2.0,double(hi[x]-hi[1])); //cout<<double(hi[x]-hi[1])<<' '<<v<<endl; if(i!=1) Addedge(x,x-m,v); if(i!=n) Addedge(x,x+m,v); if(j!=1) Addedge(x,x-1,v); if(j!=m) Addedge(x,x+1,v); dis[x]=1e50; } queue<int> q; dis[1]=0; q.push(1); inq[1]=1; while(!q.empty()) { x=q.front(); q.pop(); inq[x]=0; for(i=h[x];i;i=e[i].pre) { u=e[i].to; if(dis[u]>e[i].d+dis[x]) { dis[u]=e[i].d+dis[x]; if(!inq[u]) { q.push(u); inq[u]=1; } } } } printf("%.2fn",dis[n*m]/v0); return 0;}
