CodeForces-1139A-Even Substrings

最新推荐文章于 2021-02-21 11:29:13 发布

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最新推荐文章于 2021-02-21 11:29:13 发布

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分类专栏： ACM_刷题文章标签： CodeForces ACM acm CF NOIP

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本文介绍了一道关于字符串处理的编程题目，任务是找出给定数字字符串中所有偶数子串的数量。文章提供了完整的代码实现，采用C++语言，通过遍历字符串并判断每个字符对应的数字是否为偶数来累加答案。

题目：

Description：

You are given a string s=s1s2…sns=s1s2…sn of length nn, which only contains digits 11, 22, ..., 99.

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

Find the number of even substrings of ss. Note, that even if some substrings are equal as strings, but have different ll and rr, they are counted as different substrings.

Input

The first line contains an integer nn (1≤n≤650001≤n≤65000) — the length of the string ss.

The second line contains a string ss of length nn. The string ss consists only of digits 11, 22, ..., 99.

Output

Print the number of even substrings of ss.

Examples

input

4
1234

output

input

4
2244

output

Note

In the first example, the [l,r][l,r] pairs corresponding to even substrings are:

s[1…2]s[1…2]
s[2…2]s[2…2]
s[1…4]s[1…4]
s[2…4]s[2…4]
s[3…4]s[3…4]
s[4…4]s[4…4]

In the second example, all 1010 substrings of ss are even substrings. Note, that while substrings s[1…1]s[1…1] and s[2…2]s[2…2] both define the substring "2", they are still counted as different substrings.

题意分析：

阅读理解题，水题

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int ans=0,n;
char s[65005];
int main()
{
	scanf("%d",&n);
	scanf("%s",&s);
	for(int i=0;i<strlen(s);i++)
	{
		if((s[i]-'0')%2==0)ans+=(i+1);
	}
	printf("%d",ans);
}