答案

#include<bits/stdc++.h>
using namespace std;
int main(){
int days=0;
int coins=0;
int n=0;
int k,b;cin>>k;
while(true){
n+=1;
if (days+n<=k){
days+=n;
coins+=nn;
}
else{
b=k-days;
coins+=bn;
break;
}
}
cout<<coins;
}