This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(),x.end()
#define ll long long
#define LCBorz ios_base::sync_with_stdio(false);cin.tie(0);
const int N=1000005;
const int mod=1e6+3;
const ll INF=1e18;
int32_t main(){
LCBorz;
int n;cin>>n;
vector<ll> v(n+2),pre(n+2),suf(n+2);
for(int i=1;i<=n;i++){
cin>>v[i];
}
ll cnt=0;
vector<int> st;
int lz=0,zero=0;
for(int i=1;i<=n;i++){
if(v[i]==0){
lz^=1;
zero++;
}
else {
cnt+=zero;
if((v[i]==1)^lz){
if(st.size()&&(st.back()+i)%2==1){
cnt+=(i-st.back());
st.pop_back();
}
else{
st.push_back(i);
}
}
}
if(st.size()==0){
pre[i]=cnt;
}
else{
pre[i]=INF;
}
}
st.clear();
cnt=0;
lz=0;
zero=0;
for(int i=n;i>=1;i--){
if(v[i]==0){
lz^=1;
zero++;
}
else {
cnt+=zero;
if((v[i]==-1)^lz){
if(st.size()&&(st.back()+i)%2==1){
cnt+=(st.back()-i);
st.pop_back();
}
else{
st.push_back(i);
}
}
}
if(st.size()==0){
suf[i]=cnt;
}
else{
suf[i]=INF;
}
}
ll ans=INF;
for(int i=0;i<=n;i++){
ans=min(ans,pre[i]+suf[i+1]);
//cout<<pre[i]<<' '<<suf[i+1]<<endl;
}
if(ans==INF){
cout<<-1<<endl;
}
else{
cout<<ans<<endl;
}
return 0;
}
/*
20
1 1 1 1 1 1 1 1 1 1 1 1 -1 1 1 -1 1 -1 -1 1
4
*/
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