#include <iostream>

using namespace std;

int main()
{
    long int numOfIns, sum=0, tempsum=0;

    cin >> numOfIns;
    
    for (int i=0; i<numOfIns; i++){
        long int v;
        cin >> v;
        sum += v;
    }

    while(sum/10 != 0){ 
        
        tempsum=0;
        while(sum/10 != 0){
        
            tempsum+=(sum%10);
            sum/=10;
        }
        tempsum+=(sum%10);
        sum = tempsum;
    }
    if(sum >= 0) cout << sum;

    else if(sum < 0) cout << -1*sum;

    return 0;
}