#include <cstdio>

int main() {
	freopen("operatii.in","rt",stdin);
	freopen("operatii.out","wt",stdout);
	int n = 0, r = 0, v[2];
	scanf("%d",&n);
	scanf("%d",&v[0]);
	for (int i = 1; i<n; ++i) {
		scanf("%d",&v[i%2]);
		if (v[i%2] > v[(i-1)%2])
			r += v[i%2] - v[(i-1)%2];
	}
	printf("%d\n",r);
	return 0;
}