Fibonacci数列的计算和转换

#include<stdio.h>
#define N 30
int i=0;
int a[N];

int fun(int first, int second, int num)
{
    int temp;
    a[i] = first;
    a[i+1] = second;
    while(num --)
    {
        ++i;
        a[i+1] = a[i-1] + a[i];
    }
    return a[i-1];

}

int main()
{
    int a, b, n;
    scanf("%d %d %d", &a, &b, &n);
    printf("%d\n", fun(a, b, n));
    return 0;
}