#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

char s[312345];
int pa[312345], pb[312345], pc[312345];

int main() {
    int n;
    scanf("%s", s);
    n = strlen(s);
    for(int i = 0; i < n; i++) {
        pa[i] = i?(pa[i - 1] + (s[i] == 'A')):(s[i] == 'A');
        pb[i] = i?(pb[i - 1] + (s[i] == 'B')):(s[i] == 'B');
        pc[i] = i?(pc[i - 1] + (s[i] == 'C')):(s[i] == 'C');
        //printf(" %d %d %d ", pa[i], pb[i], pc[i]);
    }
   // putchar('\n');
   int ans = 1;
   int sa = 0, sb = 0, sc = 0;
   int p = 0;
    for(int i = 0; i < n; i++) {
      if(s[i] == 'A') {
          sa++;
      }
      if(s[i] == 'B') {
          sb++;
          
      }
      if(s[i] == 'C') {
          sc++;
      }
      int val = min(sa, min(sb, sc));
      sa -= val;
      sb -= val;
      sc -= val;
      ans = max(ans, max(sa, max(sb, sc)));
    }
    printf("%d\n", ans);

    return 0;
}