Segment（技巧 相乘转换成相加）

#include<iostream>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
const int INF = 0x3f3f3f3f;
typedef long long LL;
LL js(LL x, LL y, LL MOD){
    LL ans = 0;
    while(x){
        if(x&1){
            ans += y;
            ans %= MOD;
        }
        x >>= 1;
        y <<= 1;
        y %= MOD;
    }
    return ans;
}
int main(){
    LL P, q;
    int T;
    scanf("%d", &T);
    while(T--){
        scanf("%lld%lld", &q, &P);
        if((q - 1) & 1){
            printf("%lld\n", js(q - 1, (q - 2) / 2, P));
        }
        else if((q - 2) & 1){
            printf("%lld\n", js(q - 2, (q - 1) / 2, P));
        }
    }
    return 0;
}