#include <stdio.h>

long n,i,last,curent,sol;

int main(){
    freopen ("operatii.in","r",stdin);
    freopen ("operatii.out","w",stdout);
    
    scanf("%ld",&n);
    scanf("%ld",&last);
    for (i=2;i<=n;i++){
        scanf("%ld",&curent);
        if (last<curent)sol+=curent-last;
        last=curent;
    }
    
    printf("%ld\n",sol);
    
    return 0;
}