#include<iostream>
#include<cmath>
using namespace std;
int n,n1,a[32],b[32],m[32],ans=100,br,last;
bool a1[32];
int main()
{
    int i,j,i1;
    cin>>n;
    for(i=0;i<n;++i)
    {
        cin>>a[i];
    }
    //last=a[0];for(j=1;j<n;++j){if(a[j]==last){a1[j]=1;}last=m[j];}
    j=0;
    for(i=0;i<n;++i){if(!a1[i]){m[j]=a[i];++j;}}
    n=j;
    for(i=0;i<n;++i){if(m[i]>n1){n1=m[i];}}++n1;
    //for(i=0;i<n;++i){cout<<m[i]<<" ";}
    for(i=0;i<(pow(2,n));++i)
    {
        for(j=0;j<n;++j){a1[j]=0;}
        i1=i;
        j=n-1;
        br=0;
        while(i1>0){a1[j]=i1%2;br+=i1%2;i1/=2;--j;}
        if((br)<ans)
        {
            for(j=1;j<n1;++j){b[j]=0;}
            j=0;while(a1[j]){++j;}
            last=m[j];++b[m[j]];
            for(++j;j<n;++j)
            {
                if(!a1[j]){if(m[j]!=last){/*cout<<"fail\n";*/++b[m[j]];if(b[m[j]]>1){break;}last=m[j];}}
            }
            if(j==n){ans=br;}//for(j=0;j<n;++j){if(!a1[j]){cout<<m[j];}else{cout<<" ";}}cout<<endl;}
        }
        //for(j=0;j<n;++j){if(a1[j]){cout<<m[j];}else{cout<<" ";}}cout<<endl;
    }
    cout<<ans<<endl;
    return 0;
}
