https://old.ynoip.cn/p/7191

#include<cstdio>
using namespace std;
int road[100005];

int main(void)
{
	int n=0;
	scanf("%d",&n);
	for(int i=0;i<n;i++)
		scanf("%d",&road[i]);
	int count=0;
	count=road[0];
	for(int i=0;i<n;i++)
	{
		if(road[i]<road[i+1])
		{
			count+=road[i+1]-road[i];
		}
	}
	printf("%d",count);
	return 0;
}