#include <assert.h> #include <limits.h> #include <algorithm> #include <bitset> #include <cctype> #include <cmath> #include <complex> #include <deque> #include <functional> #include <iomanip> #include <iostream> #include <map> #include <numeric> #include <queue> #include <set> #include <stack> #include <string> #include <unordered_map> #include <vector> #include <random> #define rep(i, a, b) for (long long (i) = (a); i < (b); i++) #define all(i) i.begin(), i.end() #define debug(i) std::cerr << "debug " <<"LINE:"<<__LINE__<<" "<< #i <<":"<< i << std::endl template <typename T1, typename T2> std::ostream& operator<<(std::ostream& os, std::pair<T1, T2> pa) { return os << pa.first << " " << pa.second; } template <typename T> std::ostream& operator<<(std::ostream& os, std::vector<T> vec) { for (int i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " "); return os; } template<typename T1,typename T2> inline bool chmax(T1& a,T2 b){return a<b && (a=b,true);} template<typename T1,typename T2> inline bool chmin(T1& a,T2 b){return a>b && (a=b,true);} long long pow_mod(long long a, long long b, long long mod=-1) { if ((a == 0)||(mod!=-1&&a%mod==0)) { return 0; } long long x = 1; while (b > 0) { if (b & 1) { x = (mod!=-1)?(x * a) % mod:x*a; } a = (mod!=-1)?(a * a) % mod:a*a; b >>= 1; } return x; } // const long long MOD = 998244353; const long long MOD = 1e9 + 7; using ll = long long; using P = std::pair<ll, ll>; ll gcd(ll a,ll b){ if(a%b==0)return b; else return gcd(b,a%b); } int main() { std::cin.tie(0); std::ios::sync_with_stdio(false); ll n; std::cin>>n; std::vector<ll> b(n); rep(i,0,n)std::cin>>b[i]; ll ans=0; ll now=0; rep(i,0,n){ while(b[i]>0){ ans+=std::abs(now-i); now++; b[i]--; } } std::cout<<ans<<"\n"; return 0; }