#include <bits/stdc++.h> using namespace std; #define int long long const int N = 1e5 + 5; int n; int s[N] , h[5][N] , sum , maxn = -1; signed main() { cin >> n; for (int i = 1;i <= n;i++) cin >> s[i]; for (int i = 1;i <= n;i++) { h[0][i] = maxn; maxn = max(maxn , s[i]); } maxn = 0; for (int i = n;i >= 1;i--) { h[1][i] = maxn; maxn = max(maxn , s[i]); } for (int i = 1;i <= n;i++) { int x = min(h[1][i] , h[0][i]) - s[i]; if (x > 0) sum += x; } cout << sum; return 0; }