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#include #include #include #include #include #include #include #include using namespace std; #define inf 10000000 #define N 100050 #define ll __int64 ll n; ll a[N], lsum[N], rsum[N]; ll lok[N], rok[N]; int main(){ ll i, j; while(cin>>n) { ll sum = 0; bool siz = false; for(i=1;i<=n;i++)cin>>a[i], sum += a[i], siz |= a[i]; if(!siz) { cout<<(n-1)*(n-2)/2<