import java.io.*;
import java.util.*;

class Main {

    // Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
    public static void main(String[] args) throws Exception {
        final Scanner sc = new Scanner(System.in);
        long N;
        N = sc.nextLong();
        long[] h = new long[(int)(N)];
        for(int i = 0 ; i < N ; i++){
                h[i] = sc.nextLong();
        }
        solve(N, h);
    }

    static void solve(long N, long[] h){
	int ans = 0;
	while(!isAllZero(h)) {
	    int left = 0;
	    while(left < h.length) {
		//System.out.println(Arrays.toString(h));
		int right = left;
		while(right < h.length && h[right] != 0) { right++; }
		if (left != right) { ans++; }
		for(int i = left; i < right; i++) {
		    h[i]--;
		}
		left = right + 1;
	    }
	}
	System.out.println(ans);
    }

    static boolean isAllZero(long[] h) {
	for(long i: h) {
	    if (i != 0) {
		return false;
	    }
	}
	return true;
    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz