#include <stdio.h>
#include <stdlib.h>

int main(){
    int n, i, pr, x;
    long long rez=0LL;
    FILE*fi,*fo;
    fi=fopen("operatii.in","r");
    fo=fopen("operatii.out","w");
    fscanf(fi,"%d%d", &n, &pr);
    for(i=1;i<n;i++){
        fscanf(fi,"%d", &x);
        if(x>pr)
            rez=rez+x-pr;
        pr=x;
    }
    fprintf(fo,"%lld", rez);
    fclose(fi);
    fclose(fo);
    return 0;
}