题意:
解法:
显然答案一定是x9999的形式,从低位开始填数位,优先填大的即可.
code:
#include <bits/stdc++.h>
#define int long long
#define PI pair<int,int>
using namespace std;
const int maxm=2e5+5;
int n;
void solve(){
cin>>n;
int ans=0;
int last=0;
int p=1;
while(1){
int ok=0;
for(int i=9;i>=1;i--){
int t=i*p;
if(t+last<=n){
ans+=i;
last=t+last;
ok=1;
break;
}
}
if(!ok)break;
p*=10;
}
cout<<ans<<endl;
}
signed main(){
ios::sync_with_stdio(0);
solve();
return 0;
}