#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <ctime>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <set>
#include <vector>
#include <stack>
#include <map>
#include <string>
#include <cstring>
#include <queue>
#include <utility>
using namespace std;


#define PB push_back
#define sqr(x) (x)*(x)
long long const INF= 1ll<<32;
int price(int a,int b,int c,int len){
	int ans=0;
	if(a != 0) ans++;
	if(b-a != 1) ans++;
	if(c - b != 1) ans++;
	if(c != len -1) ans++;
	if(ans < 0) ans = 10000;
	return ans;
}
int main()
{
#ifdef HOME
	//freopen("k8.in","r",stdin);
	freopen("input.txt","r",stdin);
	//freopen("k8.out","w",stdout);
	//freopen("output.txt","w",stdout);
#else
	freopen("input.txt","r",stdin);
	freopen("output.txt","w",stdout);
#endif
	string s;
	int p1=-1,p2=-1,p3=-1;
	vector<int> ss,ii;
	cin >> s;
	transform(s.begin(),s.end(),s.begin(),::tolower);
	for(int i=0;i<s.length();i++){
		if(s[i] == 's') ss.push_back(i);
		if(s[i] == 'i') ii.push_back(i);

	}
	//while(ii.size() > 0 && ii[0] <= ss[0]) ii.erase(ii.begin());



	if(s.length() < 3 || ss.size() < 2 || ii.size() < 1 || ii[ii.size()-1] > ss[ss.size()-1] || ii[0] < ss[0])
		puts("-1");
	else{
		int ans=1000;

		for(int i=0;i<ss.size();i++)
			for(int j=0;j<ii.size();j++)
				for(int k=i+1;k<ss.size();k++)
					ans=min(ans,price(ss[i],ii[j],ss[k],s.length()));

		printf("%d\n",ans);
	}
	return 0;
}