#include <stdio.h>
 
// 再帰関数：第n項を求める
int fib(int n) {
    if (n == 0 || n == 1)
        return 1;               // a0 = 1, a1 = 1
    else
        return fib(n - 1) + fib(n - 2); // an = an-1 + an-2
}
 
int main(void) {
    int n;
 
    // 入力：非負の整数 n
    printf("非負の整数 n を入力してください: ");
    scanf("%d", &n);
 
    // 出力：第n項
    printf("a_%d = %d\n", n, fib(n));
 
    return 0;
}
 

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