自己看

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n;
string s;
int main(){
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	std::cout.tie(nullptr);
	cin>>n>>s;
    char ch='a';
    for(ll i=0;i<n;i++){
        if(s[i]>ch){
            ch=s[i];
        }
    }
    cout<<(ll)ch-96<<endl;
	//fclose(stdin);
	//fclose(stdout);
	return 0;
}
//coder::by::M91