#include <stdio.h>


int main()
{
	long long op=0,i=0,k=0, l=0, n=0;
	
	FILE *in  = fopen("operatii.in","r");
	FILE *out = fopen("operatii.out","w");
	
	fscanf(in,"%lld",&n);
	fscanf(in,"%lld",&k);
	op=k;
	for (i=1; i<n; i++)
	{
		fscanf(in,"%lld",&l);
		if (l>k)
			op+=l-k;
		k=l;
	}
	
	fprintf(out,"%lld\n",op);
	
	return 0;
}