//program to find longest repeating subsequence.

string s;

cin>>s;

int n = s.length();

int arr[n+1][n+1];

for(int i=0;i<=n;i++){

for(int j=0;j<=n;j++) arr[i][j] = 0;

}

for(int i=1;i<=n;i++){

for(int j=1;j<=n;j++){

if(s[i-1]==s[j-1] && i!=j){

arr[i][j] = 1 + arr[i-1][j-1];

}else{

arr[i][j] = max(arr[i-1][j], arr[i][j-1]);

}

}

}

cout<<arr[n][n]<<endl;

return 0;

}