1 #include "cstdio"
 2 #include "iostream"
 3 #include "algorithm"
 4 #include "string"
 5 #include "cstring"
 6 #include "queue"
 7 #include "cmath"
 8 #include "vector"
 9 #include "map"
10 #include "stdlib.h"
11 #include "set"
12 #define mj
13 #define db double
14 #define ll long long
15 using  namespace std;
16 const int N=1e6+5;
17 const int mod=1e9+7;
18 const ll inf=1e16+10;
19 char s[N];
20 int a[N];
21 int  dfs(int i,int n,int cnt){
22     if(i==n){//判断最后一张牌的状态
23         if(a[n-1]) return 1e8;
24         else return cnt;
25     }
26     if(a[i-1]) a[i-1]=!a[i-1],a[i]=!a[i],a[i+1]=!a[i+1],cnt++;
27     return dfs(i+1,n,cnt);
28 }
29 int main()
30 {
31     int n;
32     while(scanf("%s",s)==1){
33         int ans;
34         n=strlen(s);
35         for(int i=0;i<n;i++)
36             a[i]=s[i]-‘0‘;
37         a[0]=!a[0],a[1]=!a[1];
38         ans=dfs(1,n,1);
39         for(int i=0;i<n;i++)
40             a[i]=s[i]-‘0‘;
41         ans=min(ans,dfs(1,n,0));//取最小值
42         if(ans==1e8) printf("NO\n");
43         else printf("%d\n",ans);
44 
45     }
46     return 0;
47 }