#include <cstdio>

const char FIN[] = "operatii.in";
const char FOU[] = "operatii.out";
long long V, AUX , N, rez;

int main()
{
    freopen(FIN , "r" , stdin);
    freopen(FOU , "w" , stdout);

    scanf("%lld", &N);

    for (int i = 1; i <= N; AUX = V, i++)
    {
        scanf("%lld", &V);
        if ( V > AUX)
            rez += V - AUX;
    }

    printf("%lld", rez);

    return 0;
}