#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=12;
inline int read(){char c=getchar();int x=0,f=1;while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}return x*f;
}
int n,m,ans=0;
int vis[50],shift=10;
void dfs(int d){ans=max(ans,d-2);if(d>m+n) return;for(int x=1;x<=d-1;x++){int y=d-x;if(x<1||x>n||y<1||y>m) continue;//printf("dfs %d  %d %d\n",d,x,y);if(vis[x-y+shift]) continue;vis[x-y+shift]=1;dfs(d+1);vis[x-y+shift]=0;}
}int main(){freopen("bishop.in","r",stdin);freopen("bishop.out","w",stdout);n=read();m=read();dfs(2);printf("%d",ans);
}

//搜索
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=1005,INF=1e9;
inline int read(){char c=getchar();int x=0,f=1;while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}return x*f;
}
int n,s,a[N],w[N],vis[N],cnt=0,ans=1e9;
void dfs(int x,int t,int val){//printf("dfs %d %d %d\n",x,t,val);
cnt++;vis[x]=1;if(cnt==n){ans=min(ans,val);return;}int i;for(i=x+1;i<=n;i++) if(!vis[i]) break;if(i<=n){int tt=t+(a[i]-a[x]);dfs(i,tt,val+tt*w[i]);cnt--;vis[i]=0;}for(i=x-1;i>=1;i--) if(!vis[i]) break;//printf("vis %d  hi2 %d %d\n",vis[1],x,i);if(i>=1){int tt=t+(a[x]-a[i]);dfs(i,tt,val+tt*w[i]);cnt--;vis[i]=0;}
}
int main(){freopen("czybm.in","r",stdin);freopen("czybm.out","w",stdout);n=read();s=read();for(int i=1;i<=n;i++){a[i]=read();w[i]=read();}dfs(s,0,0);printf("%d",ans);
}

//区间DP#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
const int N=1005;
inline int read(){char c=getchar();int x=0,f=1;while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}return x*f;
}
int n,st,a[N],w[N],s[N];
int f[N][N][2];
inline int sum(int i,int j){return s[j]-s[i-1];}
void dp(){for(int i=1;i<=n;i++) f[i][i][0]=f[i][i][1]=abs(a[i]-a[st])*s[n];for(int l=2;l<=n;l++)for(int i=1;i<=n;i++){int j=i+l-1;if(j>n) break;f[i][j][0]=min(f[i+1][j][0]+(a[i+1]-a[i])*(sum(j+1,n)+sum(1,i)),f[i][j-1][1]+(a[j]-a[j-1])*(sum(j,n)+sum(1,i-1))+(a[j]-a[i])*(sum(1,i-1)+sum(j+1,n)) );f[i][j][1]=min(f[i][j-1][1]+(a[j]-a[j-1])*(sum(j,n)+sum(1,i-1)),f[i+1][j][0]+(a[i+1]-a[i])*(sum(1,i)+sum(j+1,n))+(a[j]-a[i])*(sum(1,i-1)+sum(j+1,n)) );}
}
int main(){//freopen("czybm.in","r",stdin);//freopen("czybm.out","w",stdout);n=read();st=read();for(int i=1;i<=n;i++){a[i]=read();w[i]=read();s[i]=s[i-1]+w[i];printf("n %d\n",i);}dp();printf("%d",min(f[1][n][0],f[1][n][1]));
}