#include <bits/stdc++.h>
using namespace std;
int main(){
    int N,count;
    long long ans=0;
    cin>>N;
    if(N==1){
    	cout<<0<<endl;
    	return 0;
    }
    int A[N],B[N];
    for(int i=0;i<N;++i){
        cin>>A[i];
        A[i]^=i%2;
    }
    A[N-1]=!A[N-2];
    for(int i=N-2;i>=0;--i){
        ++count;
        if(A[i]!=A[i+1]){
            count=1;
        }
        B[i]=count;
    }
    for(int i=0;i<N-1;++i){
        if(A[i]^(i%2)){
            ans+=B[i];
        }
    }
    cout<<ans<<endl;
}