• Source 
    1. #include<stdio.h>
    2. int main()
    3. {
    4.     long long int a,b,c,d,i,j,count=0,q,temp;
    5.     while(scanf("%lld %lld",&a,&b)==2)
    6.     {
    7.         if(a==0&&b==0)
    8.         {
    9.             break;
    10.         }
    11.         c=0;
    12.         d=0;
    13.         if(a>b)
    14.         {
    15.             temp=a;
    16.             a=b;
    17.             b=temp;
    18.         }
    19.         for(i=a; i<=b; i++)
    20.         {
    21.             j=i;
    22.             for(q=1;; q++)
    23.             {
    24.                 if(j==1)
    25.                 {
    26.                     //count++;
    27.                     break;
    28.                 }
    29.                 else if(j%2==0)
    30.                 {
    31.                     j=j/2;
    32.                     count++;
    33.                 }
    34.                 else if(j%2==1)
    35.                 {
    36.                     j=3*j+1;
    37.                     count++;
    38.                 }
    39.             }
    40.             if(c<count)
    41.             {
    42.                 c=count;
    43.                 d=i;
    44.             }
    45.             count=0;
    46.         }
    47.         if((a==1&&b==2)||(b==1&&a==2))
    48.         {
    49.             printf("Between 1 and 2, 1 generates the longest sequence of 3 values.\n");
    50.         }
    51.         else if(a==1&&b==1)
    52.         {
    53.             printf("Between 1 and 1, 1 generates the longest sequence of 3 values.\n");
    54.         }
    55.         else
    56.         {
    57.             printf("Between %lld and %lld, %lld generates the longest sequence of %lld values.\n",a,b,d,c);
    58.         }
    59.     }
    60.     return 0;
    61. }