import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) {
        FastScanner sc = new FastScanner();
        String s = sc.next();
        long counta = 0;
        long ans = 0;

        if(s.charAt(0) == 'A'){
            counta++;
        }

        for(int i=1; i<s.length(); i++){
            if(s.charAt(i) == 'A'){
                if(s.charAt(i-1) == 'A'){
                    counta++;
                }else if(s.charAt(i-1) == 'B'){
                    counta = 1;
                }else if(s.charAt(i-1) == 'C'){
                    counta++;
                }
            }else if(s.charAt(i) == 'B'){
                if(s.charAt(i-1) == 'A'){
                    
                }else if(s.charAt(i-1) == 'B'){
                    counta = 0;
                }else if(s.charAt(i-1) == 'C'){
                    
                }
            }else if(s.charAt(i) == 'C'){
                if(s.charAt(i-1) == 'A'){
                    counta = 0;
                }else if(s.charAt(i-1) == 'B'){
                    ans += counta;
                }else if(s.charAt(i-1) == 'C'){
                    counta = 0;
                }
            }
        }

        System.out.println(ans);


    }


    private static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private static boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }

}


Measured memory_bytes: 24468