#include <bits/stdc++.h>
using namespace std;
int main() {
// max distance between same element
vector<int> arr={1,1,2,2,2,1};
unordered_map<int,int> ok;
int dist=0;
for(int i=0;i<arr.size();i++){
if(ok.find(arr[i])!=ok.end()){
dist=max(dist,i-ok[arr[i]]);
}else{
ok[arr[i]]=i;
}
}
cout<<dist;
return 0;
}
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