public static int countChanges(String message) {
        String sos = "SOS";
        int count = 0;
        for (int i = 0; i < message.length(); i++) {
            if (message.charAt(i) != sos.charAt(i % 3)) count++;
        }
        return count;
    }

#!/bin/python3
s=input().strip()
print(sum(1 for i in range(len(s)) if s[i]!="SOS"[i%3]))

function main() {
    var S = readLine();
    var n = 0;
    for(var i = 0; i < S.length ; i += 3){
        if(S[i] != "S") n++;
        if(S[i + 1] != "O") n++;
        if( S[i + 2] != "S") n++;
        
    }
   console.log(n);
}

int main(){
    string s;
   char te[3];
    te[0]='S';
    te[1]='O';
    te[2]='S';
    cin >> s;int i=0,j=0,count=0;;
    while(s[i])
        {   if(j==3)j=0;
            if((s[i])!= (te[j]))count++;
            i++;j++;   
        }
    cout<<count;
    return 0;
}

puts gets.strip.each_char.with_index.map{ |c, i| (c == 'SOS'[i % 3]) ? 0 : 1 }.reduce(:+)