#include <iostream>
#include<cstring>
using namespace std;
const int maxn=85;
char s[maxn]={0};

int main() {
		cin>>s;
		int len=strlen(s);
		int value=0,sum=0;
		for(int i=0;i<len;i++){
			if(s[i]=='O')value++;
			else value=0;
			sum+=value;
		}
		cout<<sum;
	return 0;
}