function bomb(x){
   while(/1{4,}|2{4,}|3{4,}/.test(x)){
      x=x.replace(/1{4,}|2{4,}|3{4,}/g,"");
   }
   min=Math.min(min,x.length);
}
var input = require('fs').readFileSync('/dev/stdin', 'utf8');
var Arr=(input.trim()).split("\n");
var N=Arr.shift()-0;
var arr=[];
for(var i=0;i<N;i++){
   var v=Arr.shift()-0;
   arr.push(v);
}
var min=Infinity;
var str=arr.join("");
for(var i=0;i<N;i++){
   var A=arr.slice();
   var B=arr.slice();
   if(i<N-1)A[i]=A[i+1];
   if(i>0)B[i]=B[i-1];
   bomb(A.join(""));
   bomb(B.join(""));
}
console.log(min);