#include <iostream>
#include <vector>
using namespace std;
int main(){
    long long n,m;cin>>n>>m;
    vector<long long> A(n);
    for(int i = 0; n > i; i++){
        cin>>A[i];
    }
    long long mn = 0;
    long long mx = A[0]+1;
    while(mx-mn > 1){
        long long ce = (mn+mx)/2;
        long long nw = 0;
        bool ok = true;
        for(int i = 0; n > i; i++){
            if(A[i]+nw < ce){
                ok = false;
                break;
            }
            nw = A[i]+nw-ce;
        }
        if(ok){
            mn = ce;
        }else{
            mx = ce;
        }
    }
    cout << mn/m << endl;
}