#include <stdio.h>
int y,nr,n,x;
int main()
{
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);
    scanf("%d\n",&n);
    int i;
    for (i=1;i<=n;i++)
    {
        scanf("%d",&y);
        if (y>x)
        {
            nr+=y-x;
            x=y;
        }
        if (!y)
            x=0;
    }
    printf("%d\n",nr);
    return 0;
}