#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');
    for(int i = 1; i <= n/3; i++) {
        int ok = 1;
        for(int j = i * 3 - 1; j < n; j += (i * 3)) {
            int sa, sb, sc;
            if(j > i * 3 - 1) {
                sa = pa[j] - pa[j - i*3];
                sb = pb[j] - pb[j - i*3];
                sc = pc[j] - pc[j - i*3];
            }
            else {
                sa = pa[j];
                sb = pb[j];
                sc = pc[j];
            }
            if(sa > i or sb > i or sc > i) {
                ok = 0; break;
            }
        }
        if(ok) {
            printf("%d\n", i);
            return 0;
        }
    }
    return -1;///////**********;

    return 0;
}