#include<stdio.h>
#define huge long long

int main()
{
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);
    huge n;
    scanf("%lld",&n);
    huge curent,precedent;
    huge sol=0;
    for(huge i=1;i<=n;i++)
     {
         scanf("%lld",&curent);
         if(curent>precedent)
           sol=sol+curent-precedent;
         precedent=curent;
     }
    printf("%lld\n",sol);
    return 0;
}