3错了

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

double fibonacci(int n) {
    if (n <= 2) return 1.0;
    double a = 1, b = 1, c;
    for (int i = 3; i <= n; i++) {
        c = a + b;
        a = b;
        b = c;
    }
    return b;
}

int main() {
    int n;
    scanf("%d", &n);
        double result = fibonacci(n);
        printf("%.2lf", result);

    return 0;
}