#include <stdio.h>
//練習問題D
int func(int x){
	int a;
	if(x=0){
		return -1;
	}
	else
		return 3*a*(x-1)+5;
	}
 
 
int main(void) {
	int n = 3, m;
    m = func(n);
    printf("数列anについて, n=%dのときの値は%d\n", n
, m
); 	return 0;
}
 
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