#include <iostream>
using namespace std;
int a[200001]={0},n,k;
void be(){
cin>>n>>k;
for(int i=0;i<n;i++){
    cin>>a[i];
}
}
int fasor(){
int i=0,s,t;
while(i<n){s=1;t=1;
    while(s<=k && t==1){
        if(a[i]<a[i+s])t=0;
        s++;
    }
    if(t || i+s>=n)return (i+1);
    i=i+s-1;
    }
    return -1;
}
int main()
{int b;
    be();
    b=fasor();
    cout<<b;
    return 0;
}