#include<iostream>
using namespace std;
int a[100000];
int ret(int s) {
int sum = 0;
while (s > 0 || sum > 9) {
if (s == 0) {
s = sum;
sum = 0;
}
sum += s % 10;
s /= 10;
}
return sum > 9 ? ret(s) : sum;
}
int main() {
int n;
cin >> n;
int x = 0;
for (int i = 0;i < n;i++)
{
cin >> a[i];
x += a[i];
}
cout<<ret(x);
}