This is my Own Signature Solution!!! I spent 4 days just for this, and it surpassed the editorial's speed. The implementatoin is straightforward and highly intuitive. Hope you like it.

include

using namespace std;

int main(){ int t; scanf("%d", &t); long long a, b, dts, mod, ret;

while(t--) {
    scanf("%lld %lld", &a, &b); 

    ret = 0;

    //leading partial block 
    mod = a % 4;
    if(mod == 1) { ret = a + 1; a += 3; }//ret = a + 1 is key here, which reduces computational steps 
    else if(mod == 2) { ret = a + 1; a += 2; } 
    else if(mod == 3) { ++a; }

    //Full 4-blocks 
    dts = b - a + 1; 
    mod = dts / 4; 
    if(mod % 2 > 0) ret ^= 2; //xOr results in 2. 

    //Trailing partial blocks 
    mod = dts % 4; 
    if(mod == 1 || mod == 2) ret ^= b;
    else if(mod == 3) ret ^= 2; 

    printf("%lld\n", ret); 
}

return 0; 

}