#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int A[5010];
int n;
int solve(int l,int r,int h)
{
    if (l>r) return 0;
    int loc=-1,mini=1<<30;
    int sum=0;
    for (int i=l;i<=r;i++){
        if (mini>A[i])
        {
            mini=A[i];
            loc=i;
        }
            if (A[i]>h) sum++;
    }
    //if (loc==-1) return 0;
    int tmp=A[loc]-h; //即使当前最小板子已经被刷过了，也要继续递归下去，因为还可能有其他板子没刷到，h代表当前已经刷到的高度。
    if (tmp<0) tmp=0;
    return min(sum,solve(l,loc-1,max(A[loc],h))+solve(loc+1,r,max(A[loc],h))+tmp);
}
int main()
{
   // cout<< (1<<30)<<endl;
    while (scanf("%d",&n)!=EOF)
    {
        for (int i=1;i<=n;i++) scanf("%d",&A[i]);
        int ans=solve(1,n,0);
        printf("%d\n",ans);
    }
    return 0;
}