#include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define INF 1 << 29 #define LL long long int LL const MOD = 1000000007; template class SegmentTree{ int n; int realsize; T initialvalue; vector tree; public: SegmentTree(int size,T initial):realsize(size),initialvalue(initial){ n = 1; while(n < size)n *= 2; tree = vector(2*n + 1,initial); } //1-indexed void insert(int i,T data){ int ind = n+i-1; tree[ind] = data; ind >>= 1; while(ind > 0){ tree[ind] = tree[ind*2] + tree[ind*2+1]; ind >>= 1; } } void add(int i,T data){ int ind = n+i-1; tree[ind] += data; ind >>= 1; while(ind > 0){ tree[ind] = tree[ind*2] + tree[ind*2+1]; ind >>= 1; } } T get(int l,int r){ if(l > realsize || r > realsize || l <= 0 || r <= 0)return initialvalue; l = n+l-1; r = n+r-1; if(l == r)return tree[l]; int prel = l; int prer = r; T lnum = tree[l]; T rnum = tree[r]; l >>= 1; r >>= 1; while(l != r){ if(l*2 == prel){ lnum += tree[l*2+1]; } if(r*2+1 == prer){ rnum += tree[r*2]; } prel = l; prer = r; l >>= 1; r >>= 1; } return lnum+rnum; } }; int main(){ cin.tie(0); ios::sync_with_stdio(false); LL n; cin >> n; vector a(n); vector s(n); for(int i = 0; i < n; i++){ cin >> a[i]; s[i] = a[i]; } SegmentTree st(n+1,0); sort(s.begin(),s.end()); LL ans = 0; for(int i = 0; i < n; i++){ st.add(lower_bound(s.begin(),s.end(),a[i])-s.begin()+1,1); auto itr = upper_bound(s.begin(),s.end(),a[i]); LL discount = st.get(1,itr - s.begin()); ans += itr - s.begin() - discount; } cout << ans << endl; return 0; }