#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define pii              pair <int,int>
#define pll              pair <long long,long long>
#define sc               scanf
#define pf               printf
#define Pi               2*acos(0.0)
#define ms(a,b)          memset(a, b, sizeof(a))
#define pb(a)            push_back(a)
#define MP               make_pair
#define db               double
#define ll               long long
#define EPS              10E-10
#define ff               first
#define ss               second
#define sqr(x)           (x)*(x)
#define D(x)             cerr<<#x " = "<<(x)<<endl
#define VI               vector <int>
#define DBG              pf("Hi\n")
#define MOD              1000000007
#define CIN              ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define SZ(a)            (int)a.size()
#define sf(a)            scanf("%d",&a)
#define sfl(a)           scanf("%lld",&a)
#define sff(a,b)         scanf("%d %d",&a,&b)
#define sffl(a,b)        scanf("%lld %lld",&a,&b)
#define sfff(a,b,c)      scanf("%d %d %d",&a,&b,&c)
#define sfffl(a,b,c)     scanf("%lld %lld %lld",&a,&b,&c)
#define stlloop(v)       for(__typeof(v.begin()) it=v.begin();it!=v.end();it++)
#define loop(i,n)        for(int i=0;i<n;i++)
#define loop1(i,n)       for(int i=1;i<=n;i++)
#define REP(i,a,b)       for(int i=a;i<b;i++)
#define RREP(i,a,b)      for(int i=a;i>=b;i--)
#define TEST_CASE(t)     for(int z=1;z<=t;z++)
#define PRINT_CASE       printf("Case %d: ",z)
#define LINE_PRINT_CASE  printf("Case %d:\n",z)
#define CASE_PRINT       cout<<"Case "<<z<<": "
#define all(a)           a.begin(),a.end()
#define intlim           2147483648
#define infinity         (1<<28)
#define ull              unsigned long long
#define gcd(a, b)        __gcd(a, b)
#define lcm(a, b)        ((a)*((b)/gcd(a,b)))

using namespace std;

//using namespace __gnu_pbds;
//typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;


/*----------------------Graph Moves----------------*/
//const int fx[]={+1,-1,+0,+0};
//const int fy[]={+0,+0,+1,-1};
//const int fx[]={+0,+0,+1,-1,-1,+1,-1,+1};   // Kings Move
//const int fy[]={-1,+1,+0,+0,+1,+1,-1,-1};  // Kings Move
//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move
//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move
/*------------------------------------------------*/

/*-----------------------Bitmask------------------*/
//int Set(int N,int pos){return N=N | (1<<pos);}
//int reset(int N,int pos){return N= N & ~(1<<pos);}
//bool check(int N,int pos){return (bool)(N & (1<<pos));}
/*------------------------------------------------*/

#define mx 1000005

char temp[mx];
bool vis[mx];

int main()
{
vector<pii>v[2];

//    freopen("in.txt","r",stdin);
//	  freopen("out.txt","w",stdout);
//    str[0].clear();
//    str[1].clear();
    scanf(" %s",temp);
    int n;
    n=strlen(temp);

    for(int i=0; i<n; i++)
    {
        int cnt=0;
        int j=i;
        while(j<n && temp[i]==temp[j]) cnt++,j++;
        i=j-1;
        v[0].pb(pii(cnt,temp[i]-'a'));
    }

    int ans=0;
    int a=0,b=1;
    while(1)
    {
        v[b].clear();
        bool check=0;
        n=SZ(v[a]);
        if(n<=1) break;
        int mini=(*min_element(all(v[a]))).ff;
        vector<int>aaa;
        for(int i=0; i<n; i++)
        {
            if(v[a][i].ff==mini)
            {
                if(i-1>=0)
                    aaa.pb(i-1);
                if(i+1<n)
                    aaa.pb(i+1);
                vis[i]=1;
            }
        }

        for(int i=0;i<SZ(aaa);i++)
            v[a][aaa[i]].ff-=mini;

        int last=-1;

        for(int i=0; i<n; i++)
        {
            if(vis[i]==0 && v[a][i].ff>0)
            {
                if(last==-1)
                {
                    v[b].pb(v[a][i]);
                    last=i;
                }
                else
                {
                    if(v[a][last].ss==v[a][i].ss)
                    {
                        v[b].back().ff+=v[a][i].ff;
                    }
                    else
                    {
                        v[b].pb(v[a][i]);
                    }
                    last=i;
                }
            }
            vis[i]=0;
        }
        ans+=mini;
        swap(a,b);
    }

    printf("%d\n",ans);

    return 0;
}
