#include <bits/stdc++.h>
using namespace std;

#define rep(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define ALL(v) (v).begin(),(v).end()
using ll=long long int;
const int inf = 0x3fffffff; const ll INF = 0x1fffffffffffffff; const double eps=1e-12;
template<typename T>inline bool chmax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
template<typename T>inline bool chmin(T& a,T b){if(a>b){a=b;return 1;}return 0;}



int main(){
    int n;
    cin>>n;
    vector<int> a(n);
    rep(i,0,n)cin>>a[i];

    int add=0;
    ll ret=0;
    for(int i=n-1;i>=0;i--){
        if(a[i])ret+=min(add,n-1-i);
        if(i and a[i-1]!=a[i])add++;
        else add=1;
    }
    cout<<ret<<'\n';
    return 0;
}