# include <bits/stdc++.h> # define ll long long # define fi first # define se second using namespace std; const int MXN = 3e5; ll fen[300001]; map<ll, int> M; void upd(int a) { while(a <= MXN) { fen[a]++; a += a&(-a); } return; } ll qry(int a) { int res = 0; while(a > 0) { res += fen[a]; a -= a&(-a); } return res; } int main() { int N; scanf("%d", &N); vector<ll> arr(N); for(int i=0;i<N;i++) { scanf("%lld", &arr[i]); M[arr[i]] = 1; } int cnt = 1; for(auto p : M) { M[p.fi] = cnt; cnt++; } for(int i=0;i<N;i++) { arr[i] = M[arr[i]]; // cout<<arr[i]<<endl; } vector<ll> pref(N); for(int i=0;i<N;i++) { pref[i] = qry(arr[i] - 1); upd(arr[i]); } ll ans = 0ll; for(int i=0;i<=MXN;i++) fen[i] = 0; vector<ll> suff(N); for(int i=N-1;i>=0;i--) { suff[i] = qry(arr[i] - 1); upd(arr[i]); // cout<<pref[i]<<" "<<suff[i]<<endl; ans += (1ll * pref[i]) * (1ll * suff[i]); } printf("%lld\n", ans); return 0; }

Mountains.cpp: In function 'int main()':
Mountains.cpp:30:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |  scanf("%d", &N);
      |  ~~~~~^~~~~~~~~~
Mountains.cpp:34:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 |   scanf("%lld", &arr[i]);
      |   ~~~~~^~~~~~~~~~~~~~~~~