#include <cstdio>
#define NMAX 1000005

int n;
long long v[NMAX];

int main()
{
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);
long long contor=0;
scanf("%d",&n);
    for (int i = 1; i <= n; i++) 
        {
                    scanf("%lld",&v[i]);
                            if (v[i] >= v[i - 1]) contor += (v[i]-v[i-1]);
                                }
    printf("%lld\n",contor);
    return 0;
}