var stdin process.openStdin();
stdin.addListener("data", function(d) {

// note: d is an object, and when converted to a string it will
// end with a linefeed. so we (rather crudely) account for that
// with toString() and then trim()
console.log(d.toString().trim());

});

let fs = require("fs");

function longestSubstringTwoDistinct(s) {
    let maxLen = 0;
    let startIndex = 0;
    let charIndexMap = new Map();

    for (let i = 0; i < s.length; i++) {
        charIndexMap.set(s[i], i);
        if (charIndexMap.size > 2) {
            let minIndex = Math.min(...charIndexMap.values());
            charIndexMap.delete(s[minIndex]);
            startIndex = minIndex + 1;
        }
        maxLen = Math.max(maxLen, i - startIndex + 1);
    }

    return maxLen;
}

function Main(arg) {
    
    let inputString = String(arg);
  return longestSubstringTwoDistinct(inputString);
}