#include <iostream>
#include<vector>
#include<unordered_map>
using namespace std;

int main() {
	vector<int> arr={1,1,2,2,2,1};
	int dist=0;
	int maxDist=0;
	unordered_map<int,int> d;
	for(int i=0;i<arr.size();i++) {
		if(d.find(arr[i])!=d.end()) {
			dist=i-d[arr[i]];
			maxDist=max(maxDist,dist);
		}
		else {
			d[arr[i]]=i;
		}
	}
	cout<<dist<<endl;
	return 0;
}