题意超难懂，实则一道概率论的题目。求P(n)。

P(n) = n*(1+1/2+1/3+1/4+...+1/n)。

结果如果可以除尽则表示为整数，否则表示为假分数。

1 #include 
     
       2 #include 
      
        3  4 #define MAXN 25 5  6 __int64 buf[MAXN]; 7  8 __int64 gcd(__int64 a, __int64 b) { 9     if (b == 0) return a;10     else    return gcd(b, a%b);11 }12 13 int main() {14     int i, j, k, n;15     __int64 fz, fm, tmp, intr;16 17     buf[1] = 1;18     for (i=2; i<=22; ++i)19         buf[i] = i*buf[i-1]/gcd(i, buf[i-1]);20 21     while (scanf("%d", &n) != EOF) {22         fz = 0;23         fm = buf[n];24         for (i=1; i<=n; ++i)25             fz += fm/i;26         fz *= n;27         tmp = gcd(fz, fm);28         fz /= tmp;29         fm /= tmp;30         tmp = fz/fm;31         fz -= tmp*fm;32         if (fz == 0) {33             printf("%I64d\n", tmp);34             continue;35         }36         n = 0;37         intr = tmp;38         while (tmp) {39             ++n;40             tmp /= 10;41         }42         for (i=0; i<=n; ++i)43             printf(" ");44         printf("%I64d\n", fz);45         printf("%I64d ", intr);46         j = k = 0;47         while (fz) {48             ++j;49             fz /= 10;50         }51         tmp = fm;52         while (tmp) {53             ++k;54             tmp /= 10;55         }56         j = (j>k) ? j:k;57         for (i=0; i