#include "bits/stdc++.h" using namespace std; int n,a[108][2]; multiset<int>q; vector<int>c(108); signed main(){ cin >> n; for(int i=1;i<=n;i++) cin >> a[i][1] >> a[i][2]; for(int i=n,j=1;i>=1,j<=n;i--,j++){ c[j]+=a[i][1]+a[i][2]; c[j]%=10; c[j+1]+=(a[i][1]+a[i][2])/10; } for(int i=n;i>=1;i--) cout << c[i]; return 0; }