#include <cctype>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <deque>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
const int maxn = 1e5+10;
int a[maxn];
int main()
{
int n;
ll res = 0, ans = 0;
scanf("%d",&n);
for(int i=1;i<=n;++i){
scanf("%d",&a[i]);
}
for(int i=0;i<=n-1;++i){
if(a[i]+res>=a[i+1])
res += a[i]-a[i+1];
else{
ans += a[i+1]-a[i]-res; //这里要注意如果借助当前energy仍然达不到下一个塔的话,在辅助提升的情况下,要减去当前所剩的能量
res = 0;
}
}
printf("%I64d\n",ans);
return 0;
}