#include<bits/stdc++.h>

using namespace std;
typedef long long ll;

#define N 1000010
int pre[31][N], suf[31][N];
int dpp[31][N], dps[31][N];
int fib[31];
string s; int n;

int main()
{
    cin >> s; n = s.length(); s = "0" + s;

    if (n == 1) {cout << "1\n"; return 0;}

    fib[0] = fib[1] = 1;
    for (int i = 2; i <= 30; i ++)fib[i] = fib[i - 1] + fib[i - 2];
    for (int j = 0; j <= 30; j ++) 
    {
        for (int i = 0; i <= n + 1; i ++)dpp[j][i] = dps[j][i] = fib[j];
        dpp[j][0] = dps[j][n + 1] = 0;
        suf[j][n + 1] = n + 1; pre[j][0] = 0;
    }
    for (int i = 1; i <= n; i ++)
    {
        if (s[i] == 'a')
        {
            pre[1][i] = i - 1, suf[1][i] = i + 1;
            pre[0][i] = i, suf[0][i] = i;
        }
        if (s[i] == 'b')
        {
            pre[0][i] = i - 1, suf[0][i] = i + 1;
            pre[1][i] = i, suf[1][i] = i; 
        }
    }

    int ans = int(1e9);

    for (int j = 2; j <= 30; j ++)
    {
        for (int i = 1; i <= n; i ++)
        {
            pre[j][i] = pre[j - 1][pre[j - 2][i]];
            if (pre[j][i] == 0)dpp[j][i] = dpp[j - 1][pre[j - 2][i]] + dpp[j - 2][i];
        }
        for (int i = 1; i <= n; i ++)
        {
            suf[j][i] = suf[j - 2][suf[j - 1][i]];
            if (suf[j][i] == n + 1)dps[j][i] = dps[j - 2][suf[j - 1][i]] + dps[j - 1][i];
        }
        for (int i = 1; i < n; i ++) if(pre[j - 1][i] == 0 && suf[j - 2][i + 1] == n + 1)ans = min(ans, dpp[j - 1][i] + dps[j - 2][i + 1]);
        // cout << j << ' ' << ans << endl;
    }

    cout << ans << '\n';
    return 0;
}