本地成功运行，但洛谷 ide 上编译错误，求助，玄关。

#include <bits/stdc++.h>
#define LL long long
LL x, y, m, n, l;
LL a, b, c;
LL x0, y0, g;
LL tmp;
void exgcd(LL a, LL b) {
    if (b == 0) {
        x0 = 1;
        g = a;
        return;
    }
    exgcd(b, a % b);
    tmp = x0;
    x0 = y0;
    y0 = tmp - (a / b) * y0;
}

int main() {
    scanf("%lld %lld %lld %lld %lld", &x, &y, &m, &n, &l);
    a = n - m;
    b = l;
    c = x - y;
    if (a < 0) {
        a = -a;
        c = -c;
    }
    exgcd(a, b);
    if (c % g != 0) {
        puts("Impossible");
    } else {
        LL result = (c / g * x0 % (b / g) + (b / g)) % (b / g);
        printf("%lld", result);
    }
    return 0;
}