//operatii
#include<fstream.h>
long int n,nr;
int main()
{long int i,a=0,b;
ifstream f("operatii.in");
ofstream g("operatii.out");
f>>n>>a;
for(i=2;i<=n;i++)
{f>>b;
if(b>a) nr+=(b-a);
a=b;
}
g<<nr<<'\n';
f.close();
g.close();
return 0;
}