#include <bits/stdc++.h>   using namespace std;   const int INF = 1 << 29;   const int MOD = 1000000007;   bool isPowerOfTwo(long long int x) { return x && (!(x & (x - 1))); }   void fastio() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);   }   const int dx[] = {1, 0, -1, 0, 1, 1, -1, -1};   const int dy[] = {0, -1, 0, 1, 1, -1, -1, 1};   int main() {     fastio();     int t = 1;     while (t--) {       int n;       cin >> n;       string s;       cin >> s;       int ans = 0;       for (int i = 0; i < (s.length()); i++) {         int x = int(s[i]) - 48;         if (x % 2 == 0) ans += (i + 1);       }       cout << ans <<   n ;     }     return 0;   }   