#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<algorithm>

 #include<cstdlib>

 #include<cmath>

 #include<map>

 #include<vector>

 #include<stack>

 #include<queue>

 #define lson l, m, rt<<1

 #define rson m+1, r, rt<<1|1

 #define IO ios::sync_with_stdio(false);cin.tie(0);

 #define INF 0x3f3f3f3f

 #define MAXN 500010

 const int MOD=1e9+;

 typedef long long ll;

 using namespace std;

 typedef struct{

     char c;

     int num;

 }Node;

 Node node[];

 char ss[];

 int len;

 int update(int len)

 {

     int j=, flag = ;

     for(int i = ; i < len; i++){

         if(node[i].num>){//该点还有几个

             if(!flag){//第一次找到，直接赋给node[0]

                 flag = ;

                 node[j] = node[i];

             }

             else if(node[i].c == node[j].c){

                 node[j].num += node[i].num;

             }

             else{

                 node[++j] = node[i];

             }

         }

     }

     return j;

 }

 int solve()

 {

     int len = update(strlen(ss))+, cnt=;//第一次update用的是缩点前长度，得到缩点后长度

     while(len>){

         for(int i = ;i < len-; i++){

             node[i].num -= ;

         }

         node[].num--; node[len-].num--;

         len = update(len)+;

         cnt++;

     }

     return cnt;

 }

 int main()

 {

     IO;

     cin >> ss;

         int len = strlen(ss);

     for(int i = ; i < len; i++){//注意，循环里不要放strlen！！会很耗很耗时

         node[i].c = ss[i];

         node[i].num = ;

     }

     cout << solve() << endl;

     return ;

 }