#include<stdio.h>
#define max(a,b) (a>b?a:b)

FILE *fin=fopen("operatii.in","r"),
    *fout=fopen("operatii.out","w");

int N;


int main(){
    fscanf(fin,"%d",&N);
    long long cnt=0;
    int x,ant;
    ant=0;
    fscanf(fin,"%d",&x);
    for(int i=2;i<=N;i++){
        cnt+=(long long)max(0,x-ant);
        ant=x;
        fscanf(fin,"%d",&x);
    }
    cnt+=(long long)max(0,x-ant);
    fprintf(fout,"%lld\n",cnt);
    fclose(fin);
    fclose(fout);
    return 0;
}