这应该怎么做，我不会，求解啊！

求解啊拜托拜托

把printf()放到for循环大括号外面去，改为：printf("%d",(int)sum);

#include <stdio.h>
int main() {
    int n;
    scanf("%d",&n);
    double a1 = 2,b1 = 1;//a1分子，b1分母 
    double sum = 0;
    for(int i = 1; i <= n; i++){
        sum += a1/b1;
        int t = a1;
        a1 = a1+b1;
        b1 = t;
    }
    printf("%d",(int)sum);
    return 0;
}