#include<stdio.h>
#include<stdlib.h>

int g, w, eg[10001], cg[10001];

void read() {
	FILE *fin;
	int i;
	
	fin = fopen("energii.in","r");
	fscanf(fin,"%d",&g);
	fscanf(fin,"%d",&w);
	
	for(i = 0; i < g; i++)
		fscanf(fin,"%d %d",&eg[i],&cg[i]);

		fclose(fin);	
}

int existaSol(){
	int s = 0, i;
	
	for(i = 0; i < g; i++) {
		s += eg[i];
		if(s >= w)
			return 1;
	}
	
	return 0;
}

void solve() {
	FILE *fout;
	
	fout = fopen("energii.out","w");
	
	if (!existaSol()) {
		fprintf(fout,"-1");
		fclose(fout);
		return;
	}
	else {}

	fclose(fout);
}

int main() {
	
	read();
	solve();
	return 0;
}