1420

#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

int main() {
    ifstream fin("input.txt");
    ofstream fout("output.txt");

    const int INF = 1e9;
    string strA, strB;
    fin >> strA;
    int nA = strA.size();
    int nB = 3;
    strA += 'A';
    strB = "sisA";
    vector<vector<int>> dp(nA + 2, vector<int>(nB + 2, INF));
    dp[0][0] = 0;
    for (int i = 0; i <= nA; i++)
        for (int j = 0; j <= nB; j++) {
            if (strA[i] == strB[j])
                dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j]);
            for (int k = i + 1; k <= nA; k++)
                dp[k][j] = min(dp[k][j], dp[i][j] + 1);
        }

    fout << (dp[nA][3] == INF ? -1 : dp[nA][3]) << endl;


    fin.close();
    fout.close();
    return 0;
}