#include<bits\stdc++.h>usingnamespace std;constint N =5001;int a[N];int dp[N][N];intmain(){int n;
cin >> n;for(int i =1; i <= n ; i++){
cin >> a[i];}
n =unique(a+1, a+1+n)-(a+1);for(int len =2; len <= n ; len++){for(int l =1, r = len ; r <= n ; l++, r++){if(a[l]== a[r]){
dp[l][r]= dp[l+1][r-1]+1;}else{
dp[l][r]=min(dp[l+1][r], dp[l][r-1])+1;}}}
cout << dp[1][n]<< endl;return0;}