斐波那契额数列兔子问题

#include<stdio.h>
int main()
{
int a = 1, b = 1, n, sum = 0, i = 2;
scanf("%d",&n);
if(n == 1)
{printf("1");}
else
{
while(sum < n)
{
sum = a + b;
a = b;
b = sum;
i++;
}
printf("%d\n",i);
}
return 0;
}