#include <stdio.h>

int main()
{
    int i, N, xprev, xnow;
    long long sol = 0;

    freopen("operatii.in", "r", stdin);
    freopen("operatii.out", "w", stdout);

    scanf("%d%d", &N, &xnow);
    for (i = 2; i <= N; i ++)
    {
        xprev = xnow;
        scanf("%d", &xnow);
        if (xnow < xprev)
            sol += xprev - xnow;
    }

    printf("%lld", sol + xnow);
    return 0;
}