#include<stdio.h>
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define f(i,x,n) for (int i = x;i < n;++i)
 
map<int, int> mp;
 
int main() {
	int n, mx = 0;
	scanf("%d", &n);
	f(i, 0, n) {
		int t;
		scanf("%d", &t);
		if (t >= mx)mx = t;
		else --mp[mx], ++mp[t];
	}
	int an = 0, k = 0, b = 0;
	for (map<int, int> ::iterator it = mp.begin(); it != mp.end(); ++it) {
		if (k)an += it->first - b;
		k += it->second;
		b = it->first;
	}
	printf("%d", an);
} 

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