B - 母牛的故事

#include<stdio.h>
int main()
{
  int f1, f2, f3,f4,n,t;
  while (scanf("%d", &n) != EOF)
  {
    int o = 4;
    f1 = 3;
    f2 = 2; 
    f3 = 1;
    if (n == 0)break;
    if (n == 1)
      printf("1\n");
    if (n == 2)
      printf("2\n"); 
    if (n == 3)
      printf("3\n"); 
    if (n > 3 && n < 55)
    {
      while (o<=n)
      {
        f4 = f1 + f3;
        t = f1;
        f1 = f4;
        f3 = f2;
        f2 = t;
        o++;
      }
    printf("%d\n", f4);
    }
  }
  return 0;
}