#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;
}
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