#include<bits/stdc++.h> using namespace std; int main(){ int n,x,m,d=1; int s[105]; cin>>n>>x>>m; for(int i=1;i<=n;i++){ cin>>s[i]; } while(1){ if(x-d>=1&&s[x-d]!=0&&s[x-d]<=m){ cout<<d*10; return 0; } if(x+d<=n&&s[x+d]!=0&&s[x+d]<=m){ cout<<d*10; return 0; }d++; } return 0; }