~cpp
//1. 3n+1 [[[[AOI]]]]
#include<iostream.h>
int check(int n);
void main()
{
int n1; // 1
int n2; // 2
int max=0; //길 길 .
cout<<" ( .n1<n2 )"<<endl;
cin>>n1;
cin.get();
cin>>n2;
int temp = n2;
for(int i= n2-n1 ; i >=0 ; i--)
{
if(check(temp)>max)
max = check(temp);
temp--;
}
cout<<""<<n1<<"과"<<n2<<" 길"<<max<<"."<<endl;
}
int check(int n)// 길
{
int count = 1;// 길
while(n!=1)
{
int temp = n%2;
if(temp==0)//temp값 ..
n = n/2;
else //temp값 ..
n = ((3*n)+1);
count++;
}
return count;
}










