Segment---hdu5666（两个long long 数相乘对long long求余）

#include <iostream>
#include <vector>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <algorithm>
#include <math.h>
using namespace std;
#define N 1050
#define PI 4*atan(1)
#define met(a, b) memset(a, b, sizeof(a))

typedef long long LL;

LL Mul(LL x, LL y, LL Mod)
{
    if(y == 0) return 0;

    LL ans = 2 * Mul(x, y/2, Mod)%Mod;

    if(y%2)
        ans = (ans+x)%Mod;

    return ans;
}

int main()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        LL ans, p, q, n, mod;
        scanf("%I64d %I64d", &n, &mod);
        p = n-1; q = n-2;
        if(p&1)
            ans = Mul(p, q/2, mod);
        else
            ans = Mul(p/2, q, mod);
        printf("%I64d\n", ans);
    }
    return 0;
}