#include <iostream>
#include <vector>
#include <algorithm>
#include <atcoder/modint>
using namespace std;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
#define rep(i,n) for(int i=0; i<(n); i++)


using m32 = atcoder::static_modint<998244353>;


int main(){
    int N; cin >> N;
    vector<int> A(N);
    rep(i,N) cin >> A[i];
    
    vector<int> ans(N);
    int wall[2] = { N-1, N-1 };
    for(int i=N-1; i>=0; i--){
        wall[A[i] ^ (i%2)] = i;
        ans[i] = wall[i%2] - i;
    }
    
    i64 sumans = 0;
    for(auto a : ans) sumans += a;
    cout << sumans << endl;
    return 0;
}




struct ios_do_not_sync {
    ios_do_not_sync() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} ios_do_not_sync_instance;