/*
TASK:lift
LANG:C++
*/
#include <iostream>
#include <algorithm>
using namespace std;
struct man {int v; int k; int m;};
int main(){
    int n,t,s,f,x,ff,fff,p,nn;
    man a[15],a1,a2;
    f=0;
    s=0;
    cin>>n>>t;
    for (int i=0; i<n; i++){
        cin>>a[i].v>>a[i].k;
        a[i].m=0;
        if (a[i].k>t) f=1;
        s=s+a[i].k;
        if (s>n*t/2) f=1;
    }
    if (f==1) cout<<0;
    else cout<<480;
}
