Helping Cicada

#include <cstdio>
#define ll long long
long long int ans;
long long int gcd(long long int a, long long int b) {
    while(b)
        b ^= a ^= b ^= a %= b;
    return a;
}
long long int lcm(ll int a, long long int b) {
    return a*b/gcd(a,b);
}
long long int recurs(ll int ara[], ll i, ll j, ll num, ll numofele, ll n) {
    if (numofele == num) return 0;
    ll x, y;
    for (x = i; x <numofele; x++) {
        y = lcm(ara[x], j);

        if ((num+1) & 1) ans+=(n/y);
        else ans-=(n/y);
        recurs(ara, x+1, y, num+1, numofele, n);
    }
}
int main() {
    int T;
    int cs =1;
    scanf("%d", &T);
    while (T--) {
        long long int n, m, i;
        scanf("%lld %lld", &n, &m);
        long long int ara[m];
        for (i=0; i<m; i++) scanf("%lld", &ara[i]);
        ans = 0;
        recurs(ara, 0, 1, 0, m, n);
        printf("Case %d: %lld\n",cs++, n-ans);
    }
    return 0;
}