#include<bits/stdc++.h>
using namespace std;
string s;
long long n,ans,sum;
bool fh=true;
int main()
{
	cin>>n;
	getchar();
	getline(cin,s);
	for (int i=0;i<=s.length();++i)
	{
		if (s[i]==' '||s[i]=='\0')
		{
			if (fh) ans+=sum;
			else ans-=sum;
			fh=true;
			sum=0;
		}
		else
		{
			if (s[i]=='-') fh=false;
			else
			{
				sum=sum*10+(s[i]-48);
			}
		}
	}
	cout<<ans;
	return 0;
}