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#include<bits/stdc++.h>
#define int long long
#define INF 0x3f3f3f3f
#define INFSHORT 1e+3
#define INFINT 1e+10
#define INFLONGLONG 1e+19
using namespace std;
char a[1919180];
double sum,l;
signed main(){
	while(cin>>a){
		sum+=strlen(a);
		l++;
	}
	cout<<fixed<<setprecision(1)<<sum/l;
	return 0;
}