Help in the problem, two pointers 2G

[quantavoid11]

Can anyone help me solve this problem, I have coded it using stack but it's giving the wrong answer on some test case.

#include <bits/stdc++.h>
using namespace std;
typedef long long int lli;
lli gcd(lli a, lli b)
{
if (a % b == 0)
return b;
return gcd(b, a % b);
}
class stk
{
stack<pair<lli, lli>> st;

public:
stk()
{
}
void push(lli val)
{
lli elem = st.empty() ? val : gcd(val, st.top().second);
st.push({val, elem});
}
void pop()
{
st.pop();
}
pair<lli, lli> top()
{
return st.top();
}
int size()
{
return st.size();
}
};

void remove(stk &st1, stk &st2)
{

    while (st1.size() > 0)
    {
        st2.push(st1.top().first);
        st1.pop();
    }

st2.pop();
swap(st1,st2);

}

int main()
{

int n;

cin >> n;
vector<lli> arr(n);
for (int i = 0; i < n; i++)
{
    cin >> arr[i];
}

int l = 0;
int res = INT_MAX;
stk st1, st2;
for (int r = 0; r < n; r++)
{
    st1.push(arr[r]);
    if (arr[r] == 1)
    {
        res = 1;
        break;
    }
    while (st1.size()>0&&st1.top().second == 1)
    {
        res = min(res, r - l + 1);
        remove(st1, st2);
        l++;
        // st1.pop();
    }
    
    
}

if (res > n)
{
    cout << -1;
}
else
{
    cout << res;
}

return 0;

}
Here is my implementation for the same.