序列的第k个数

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int MOD = 200907;
LL msc(LL a, LL b) {
    LL ans = 0;
    while (b) {
        if (b & 1) ans = (ans + a) % MOD;
        b >>= 1;
        a = (a + a) % MOD;
    }
    return ans;
}
LL ksm(LL a, LL b) {
    LL ans = 1;
    while (b) {
        if (b & 1) ans = (ans * a) % MOD;
        b >>= 1;
        a = (a * a) % MOD;
    }
    return ans;
}
LL arithmetic(LL first, LL k, LL d) {
    return (first + msc(--k, d)) % MOD;
}
LL proportional(LL first, LL k, LL q) {
    return msc(first, ksm(q, k - 1));
}
int main() {
    LL a, b, c, k;
    int t;
    cin >> t;
    while (t--) {
        cin >> a >> b >> c >> k;
        if (c - b == b - a) {
            LL d = c - b;
            cout << arithmetic(a, k, d) << endl;
        }
        else {
            LL q = c / b;
            cout << proportional(a, k, q) << endl;
        }
    }
    return 0;
}