#pragma GCC optimize("O3") #include using namespace std; using ll=long long; using P=pair; template using V=vector; #define fi first #define se second #define all(v) (v).begin(),(v).end() const ll inf=(1e18); //const ll mod=998244353; const ll mod=1000000007; const vector dy={-1,0,1,0},dx={0,-1,0,1}; ll GCD(ll a,ll b) {return b ? GCD(b,a%b):a;} ll LCM(ll c,ll d){return c/GCD(c,d)*d;} struct __INIT{__INIT(){cin.tie(0);ios::sync_with_stdio(false);cout< bool chmax(T &a, const T &b) { if (a bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; } templatevoid debag(const vector &a){cerr<<"debag :";for(auto v:a)cerr<void print(const vector &a){for(auto v:a)cout<>n; V a(n); for(int i=0;i>a[i]; } int c=a.back()^1; ll ans=0; ll sum=0; for(int i=n-2;i>=0;i--){ if(c!=a[i]){ sum=0; c=a[i]; } sum++; if(a[i])ans+=sum; c^=1; } cout<