#include<cstdio>

#include<algorithm>

#include<cstring>

#include<iostream>

#include<cmath>

#include<cctype>

#include<set>

#include<queue>

#include<vector>

#include<map>

using namespace std;

typedef long long LL;

inline int read() {

    int x=,f=;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-;

    for(;isdigit(ch);ch=getchar())x=x*+ch-'';return x*f;

}

const int N = ;

int f[N][N][], a[N], b[N];

int dp(int l,int r,int p) {

    if (l > r) return ;

    if (l == r) return ;

    if (f[l][r][p]) return f[l][r][p];

    int &res = f[l][r][p];

    if (p == ) {

        res = dp(l + , r, ) + (a[l + ] != a[l]);

        res = min(res, dp(l + , r, ) + (a[r] != a[l]));

    }

    else {

        res = dp(l, r - , ) + (a[l] != a[r]);

        res = min(res, dp(l, r - , ) + (a[r - ] != a[r]));

    }

    return res;

}

int main() {

    int n = read();

    for (int i = ; i <= n; ++i) a[i] = read();

    int cnt = ;

    for (int i = ; i <= n; ++i) if (a[i] != a[i - ]) b[++cnt] = a[i];

    n = cnt;

    for (int i = ; i <= n; ++i) a[i] = b[i];

    cout << min(dp(, n, ), dp(, n, ));

    return ;

}