#include <stdio.h>
int main()
{
    int n;
    int i;
    double result;
    int sign;  // 用来控制正负号
 
    result = 0;
    printf("请输入n：");
    scanf("%d", &n);
 
    for(i = 1; i <= n; i++)
    {
        if(i % 2 == 1)
        {
            sign = 1;   // 奇数项：正
        }
        else
        {
            sign = -1;  // 偶数项：负
        }
        result = result + sign * 1.0 / i;
    }
    printf("结果 = %.4f\n", result);
    return 0;
}

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9