【cf789C】Functions again（最大子序列和）

const int N=101000;
ll n,a[N],s;
ll ans,mb,mc;
int main() {
	scanf("%lld",&n);
	rep(i,0,n){
		scanf("%lld",a+i);
		if(i){
			s+=abs(a[i-1]-a[i])*(i&1?1:-1);
			mc=min(-s,mc);				
			mb=min(s,mb);
			ans=max(s-mb,ans);
			ans=max(-s-mc,ans);
		}
	}
	printf("%lld\n",ans);
	return 0;
}