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export default function countRoutes(    locations: number[],    start: number,    finish: number,    fuel: number,): number {    const MOD = 1000000007;
    const n = locations.length;    const startPos = locations[start];    const finishPos = locations[finish];
    locations.sort((a, b) => a - b);    for (let i = 0; i < n; ++i) {        if (startPos == locations[i]) {            start = i;        }        if (finishPos == locations[i]) {            finish = i;        }    }
    const dpL = Array(n)        .fill(0)        .map(() => Array<number>(fuel + 1).fill(0));    const dpR = Array(n)        .fill(0)        .map(() => Array<number>(fuel + 1).fill(0));
    dpL[start][0] = dpR[start][0] = 1;
    for (let used = 0; used <= fuel; ++used) {        for (let city = n - 2; city >= 0; --city) {            const delta = locations[city + 1] - locations[city];            if (used >= delta) {                dpL[city][used] =                    ((((used == delta ? 0 : dpL[city + 1][used - delta]) * 2) %                        MOD) +                        dpR[city + 1][used - delta]) %                    MOD;            }        }        for (let city = 1; city < n; ++city) {            const delta = locations[city] - locations[city - 1];            if (used >= delta) {                dpR[city][used] =                    ((((used == delta ? 0 : dpR[city - 1][used - delta]) * 2) %                        MOD) +                        dpL[city - 1][used - delta]) %                    MOD;            }        }    }
    let ans = 0;    for (let used = 0; used <= fuel; ++used) {        ans += (dpL[finish][used] + dpR[finish][used]) % MOD;        ans %= MOD;    }    if (start == finish) {        ans = (ans + MOD - 1) % MOD;    }    return ans;}