#include <cstdio>
int main(){
    int n, y, i, x;
    long long ans;
    FILE *fin, *fout;
    fin=fopen("operatii.in", "r");
    fout=fopen("operatii.out", "w");
    fscanf(fin, "%d", &n);
    y=ans=0;
    for(i=1; i<=n; i++){
        fscanf(fin, "%d", &x);
        if(x>y) ans+=x-y;
        y=x;
    }
    fprintf(fout, "%lld\n", ans);
    fclose(fin);
    fclose(fout);
    return 0;
}