#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N; cin >> N;
    vector<int> A(N);
    rep(i,N) cin >> A[i];
    auto B = A;
    rep(i,N) if(i & 1) B[i] ^= 1;
    vector<int> C(N, 0);
    for(int i = N - 2; i >= 0; i--) {
        if(B[i] == B[i + 1]) {
            C[i] = C[i + 1] + 1;
        } else {
            C[i] = 1;
        }
    }
    
    int ans = 0;
    rep(i,N) if(A[i]) ans += C[i];
    cout << ans << endl;
}