#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops,no-stack-protector")
#pragma GCC target("sse,sse2,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
long long gcd(long long a, long long b) { return (!b ? a : gcd(b, a % b)); }
long long lcm(long long a, long long b) { return ((a * b) / gcd(a, b)); }
const long long mod = 1e9 + 7;
const long long MOD = 998244353;
const int INF32 = 1 << 30;
const long long INF64 = 1LL << 60;
const long double pi = 3.141592653589793;
long long modpow(long long n, long long k, long long mod) {
  if (k == 0) return 1;
  long long r = modpow(n * n % mod, k >> 1, mod);
  if (k & 1) r = r * n % mod;
  return r;
}
long long dy[6] = {1, 1, 0, -1, -1, 0};
long long dx[6] = {1, 0, -1, -1, 0, 1};
void solve() {
  int n;
  string s;
  cin >> n >> s;
  long long ans = 0;
  long long cur = 0;
  vector<int> hist(n, 0);
  for (int i = 0; i < n; i++) {
    if (s[i] == '0')
      ans += cur;
    else {
      int l = i, r = i;
      while (r < n - 1 && s[r + 1] == '1') r++;
      for (int x = 1; x <= r - l + 1; x++) {
        cur += (l + x) - hist[x];
        ans += cur;
        hist[x] = r - x + 2;
      }
      i = r;
    }
  }
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  solve();
  return 0;
}
