每次删除字典序最大的字母即可,因为删除字典序最大的字母不会影响到其他字母。每次删除后更新字符串
#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;
}