### 1139 A Even Substrings

cf传送门：Even Substrings
vj传送门：Even Substrings

#### 题目描述

You are given a string s=s1s2…sn of length n, which only contains digits 1, 2, ..., 9.

A substring s[l…r] of s is a string slsl+1sl+2…sr. A substring s[l…r] of s is called even if the number represented by it is even.

Find the number of even substrings of s. Note, that even if some substrings are equal as strings, but have different l and r, they are counted as different substrings.

Input
The first line contains an integer n (1≤n≤65000) — the length of the string s.

The second line contains a string s of length n. The string s consists only of digits 1, 2, ..., 9.

Output
Print the number of even substrings of s.

Examples
Input
4
1234
Output
6
Input
4
2244
Output
10
Note
In the first example, the [l,r] pairs corresponding to even substrings are:

s[1…2]
s[2…2]
s[1…4]
s[2…4]
s[3…4]
s[4…4]
In the second example, all 10 substrings of s are even substrings. Note, that while substrings s[1…1] and s[2…2] both define the substring "2", they are still counted as different substrings.

#### 代码实现

#include<iostream>
#include<string>
using namespace std;
int main()
{
int n;
string s,l;
cin>>n>>s;
int ans=0;
for(int i=0;i<n;i++)
{
if((s[i]-'0')%2==0)
ans+=(i+1);
}
cout<<ans<<endl;
return 0;
}