codeforces 1321C（贪心）

#include<bits/stdc++.h>
#define x first
#define y second
#define PB push_back
#define mst(x,a) memset(x,a,sizeof(x))
#define all(a) begin(a),end(a)
#define rep(x,l,u) for(ll x=l;x<u;x++)
#define rrep(x,l,u) for(ll x=l;x>=u;x--)
#define sz(x) x.size()
#define IOS ios::sync_with_stdio(false);cin.tie(0);
using namespace std;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef pair<char,char> PCC;
typedef long long ll;
typedef pair<ll,ll> PLL;
const int N=105;
const int M=1e5+10;
const int INF=0x3f3f3f3f;
const int MOD=1e9+7;
bool st[N];
void solve(){
    int n;
    string s;
    cin>>n>>s;
    string buf=s;
    string res=s;
    sort(all(buf));
    int ans=0;
    int idx=n-1;
    rep(i,0,n){
        mst(st,false);
        rep(j,0,sz(res)){
            if(res[j]==buf[idx]){
                if(j>0 && abs(res[j]-res[j-1])==1 || j<n && abs(res[j]-res[j+1])==1){
                    ans++;
                    st[j]=true;
                }
            }
        }
        string f;
        rep(j,0,sz(res)) if(!st[j]) f+=res[j];
        res=f;
        idx--;
    }
    cout<<ans<<endl;
}
int main(){
    IOS;
    //freopen("test.txt", "r", stdin);
    //freopen("test.txt", "w", stdout);
    //int t;cin>>t;
    //while(t--)
        solve();
    return 0;
}