//use pascal triangle logic
#include<iostream>
#include<bits/stdc++.h>
using namespace std;
int main()
{
vector<int>arr{1,2,3,4};
/* 4 5 6 7 //only take right most digit of the adjacent number when adding
9 11 13
10 4
4
*/
int n=arr.size();
vector<vector<int>>res;
res.push_back(arr);
for(int i=0;i<n;i++)
{
vector<int>ans;
for(int j=0;j<res[i].size()-1;j++)
{
int sum=res[i][j]+res[i][j+1];
sum=sum%10;
ans.push_back(sum);
}
res.push_back(ans);
}
string r=to_string(res[n-2][0]);
r+=to_string(res[n-2][1]);
cout<<r;
}