#include <bits/stdc++.h> using namespace std; #define int long long #define double long double #define f first #define s second #define pb push_back #define yes cout << "yes" << endl; #define YES cout << "YES" << endl; #define no cout << "no" << endl; #define NO cout << "NO" << endl; void never_give_up() { int n; cin >> n; vector<int>vt(n + 1); for(int i = 1;i <= n; i++){ cin >> vt[i]; } int cvb = 0; for(int i = n; i >= 2; i--){ if(vt[i] >= vt[i - 1]){ int k = vt[i] - vt[i - 1] + 1; for(int j = i - 1; j >= 1; j--){ vt[j] += k; } cvb += k; //cout << i << " " << k << endl; } /*cout << i << " : "; for(int j = 1;j <= n; j++){ cout << vt[j] << " "; } cout << endl;*/ } cout << cvb << endl; } void You_can_do_it() { //cout << 4096 + 512 + 256 + 128; } signed main() { ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); int THE_wasd = 1; //cin >> THE_wasd; while(THE_wasd--){ never_give_up(); //You_can_do_it(); } } //1 2 4 8 16 32 64 128 256 512 1024 2048 4096