#include <stdio.h>
int e[1000005];
int main()
{
	int n,a,i,j,d=0;
	FILE *f1,*f2;
	f1=fopen("operatii.in","r");
	f2=fopen("operatii.out","w");
	fscanf(f1,"%d",&n);
	for(i=1;i<=n;i++)
	{
		fscanf(f1,"%d",&e[i]);
	}
	for(i=1;i<=n;i++)
	{
			while(e[i]!=0)
			{
				for(j=i;j<=n;j++)
				{
						if(e[j]!=0)	e[j]--;
						else	break;
				}
				d++;
			}
	}
	fprintf(f2,"%d",d);
	fclose(f1);
	fclose(f2);

	return 0;
}