#include<stdio.h>
const int N = 1e5 + 5;

long long n, m, a[N];

bool A(long long x)
{
    long long b[N] = {0};
    long long i, k, z;
    for(i = 0, k = m; i < n - 1; i++)
    {
        if(b[i] >= x)
        {
            if(k > 0)
                k--;
            else
                return 0;
            continue;
        }
        z = x - b[i];
        if(z % a[i])
            z = z / a[i] + 1;
        else
            z = z / a[i];

        if(k < z * 2 - 1)
            return false;
        k -= z * 2 - 1;
        b[i+1] += (z-1) * a[i+1];
    }
    if(b[i] < x)
    {
        z = x - b[i];
        if(z % a[i])
            z = z / a[i] + 1;
        else
            z = z / a[i];
        if(k < z * 2 - 1)
            return false;
    }
    return true;
}

int main()
{
    long long t, i, x, r, l;
    scanf("%lld", &t);
    while(t--)
    {
        scanf("%lld%lld", &n, &m);
        r = 1e17;
        for(i = 0; i < n; i++)
        {
            scanf("%lld", &a[i]);
            if(r > a[i] * m)
                r =  a[i] * m;
        }
        l = 0;
        while(r - l > 1)
        {
            x = (r + l) / 2;
            if(A(x))
                l = x;
            else
                r = x;
        }
        if(A(r))
            printf("%lld\n", r);
        else
            printf("%lld\n", l);
    }
    return 0；
}

answer.code: In function ‘int main()’:
answer.code:72:12: error: unable to find numeric literal operator ‘operator""；’
   72 |     return 0；
      |            ^~~
answer.code:72:12: note: use ‘-fext-numeric-literals’ to enable more built-in suffixes
answer.code:72:15: error: expected ‘;’ before ‘}’ token
   72 |     return 0；
      |               ^
      |               ;
   73 | }
      | ~              
answer.code:47:10: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   47 |     scanf("%lld", &t);
      |     ~~~~~^~~~~~~~~~~~
answer.code:50:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   50 |         scanf("%lld%lld", &n, &m);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~
answer.code:54:18: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   54 |             scanf("%lld", &a[i]);
      |             ~~~~~^~~~~~~~~~~~~~~