关于斐波那契数列的代码问题！！！

Question

具体问题如图所示，用函数写这个代码，拜托各位大神！！

Answer 1

 #include "stdio.h"
int f(int n)
{
if (n == 1 || n == 2) return 1;
return f(n - 2) + f(n - 1);
}
int main()
{
int m, n;
int sum = 0;
scanf("%d %d", &m, &n);
for (int i = m; i <= n; i++)
sum += f(i);
printf("%d\n", sum);
}