/*
Given a string, find the length of the longest substring which has no repeating characters.

Input format
Input is a string.

Output format
Output is an integer representing the longest substring with no repeating characters.

Sample Input 1
aabcccbcb

Sample Output 1
3

Explanation 1
"abc" is the longest substring with no repeating characters.

Sample Input 2
cdddddd

Sample Output 2
2

Explanation 2
"cd" is the longest substring with no repeating characters.
*/

/**
 * @param {string} str
 * @return {number}
 */
// please check general approach of this video: https://www.youtube.com/watch?v=Lav6St0W_pQ
function longestSubstringWithoutRepeatingCharacter(str) {
    let i,j,currLongestSubstring,longestSubstring,n;
    i=0;
    j=0;
    currLongestSubstring='';
    longestSubstring='';
    n=str.length;
    const mp= new Map();
    while(j<n){
        const currChar=str.charAt(j);
        if(!mp.has(currChar)){
            mp.set(currChar,true);
            currLongestSubstring=str.slice(i,j+1);
            if(currLongestSubstring.length>longestSubstring.length)
              longestSubstring=currLongestSubstring;
        }
        else{
            while(mp.has(currChar)){
                mp.delete(str.charAt(i));
                i++;
            }
            mp.set(currChar,true);// j-th index character
            currLongestSubstring=str.slice(i,j+1);
            if(currLongestSubstring.length>longestSubstring.length)
              longestSubstring=currLongestSubstring;
        }
        j++;
    }
    return longestSubstring.length;

}

function main() {
    let s = readLine();
    let result = longestSubstringWithoutRepeatingCharacter(s);
    console.log(result);
}