#include<bits/stdc++.h>
using namespace std;
int main(){
long long n,d,k,a,b;
cin>>n>>d;
k=n/d;
a=k*d;
b=a+d;
if(a==n){
cout<<a;
}
else if(n-a<b-n){
cout<<a;
}
else if(n-a>b-n) {
cout<<b;
}
else{
cout<<a;
}
return 0;
}

发错皆！

别怪我没告诉你，上面是错的

#include<bits/stdc++.h>
using namespace std;
int main()
{
int n,m,j1,j2,nt,nt1;
cin>>n>>m;
n=nt;
n=nt1;
while(j1!=0)
{
nt=nt-1;
j1=nt%m;
}
while(j2!=0)
{
nt1=nt1+1;
j2=nt1%m;
}
if(nt>nt1)
cout<<nt1;
else
cout<<nt;
return 0;
}