加油

#include<bits/stdc++.h>
using namespace std;

int main(){
priority_queue<int,vector<int>,less<int>>q;
int n,m;
cin>>n>>m;
long long sum = 0,ans = 0;
for(int i = 1;i <= n;i++){
int x,y;
cin>>x>>y;
sum += x;
ans += y;
q.push(x - y);
}
if(ans > m){
cout<<"-1";
return 0;
}
long long cnt = 0;
while(sum > m){
sum -= q.top();
cnt++;
}
cout<<cnt;
return 0;
}