#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
int a[5678];
int dfs(int l,int r,int k)
{
    if(l>r||(l==r&&a[l]<=k)) return 0;
    if(l==r) return 1;
    //注意区间左闭右开 只有这里r+1考虑右边界
    int mn=min_element(a+l,a+r+1)-a;
    //注意-k
    return min(r-l+1,dfs(l,mn-1,a[mn])+dfs(mn+1,r,a[mn])+a[mn]-k);
}
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        memset(a,0,sizeof(a));
        for(int i=0;i<n;i++)
        scanf("%d",&a[i]);
        //区间严格[l,r]
        //如果用0,n注意所有地方都要改
        printf("%d\n",dfs(0,n-1,0));
    }
    return 0;
}

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
using namespace std;
int n,a[100005];
int get(int l,int r)
{
    int minn=1e9+3;
    for(int i=l;i<=r;i++)
    {
        minn=min(minn,a[i]);
    }
    int ans=minn;
    for(int i=l;i<=r;i++)
    {
        if(a[i]==minn)
            continue;
        int ii=i+1;
        while(ii<=r&&a[ii]!=minn)
            ii++;
        ii--;
        for(int j=i;j<=ii;j++)
            a[j]-=minn;
        ans+=get(i,ii);
        i=ii;
    }
    return min(r-l+1,ans);
}
int main()
{
    //freopen("in.txt", "r", stdin);
    while(~scanf("%d",&n))
    {
        for(int i=0;i<n;i++)
        {
            scanf("%d",&a[i]);
        }
        printf("%d\n",get(0,n-1));
    }
    return 0;
}