#include<cstdio>
using namespace std;
FILE *in,*out;

const int N = 1010;
const int M= 25001;
int P[N],dmin[M],C[N], minim = 1<<28;
inline int min(int a, int b){
    return a < b ? a : b;
}

int main(){
    in=fopen("energii.in","r");
    out=fopen("energii.out","w");

    int n,W,sum=0;
    fscanf(in,"%d%d",&n,&W);
    for(int i=1;i<=n;++i){
        fscanf(in,"%d%d",&P[i],&C[i]);
        sum+=P[i];
    }
    if(sum<W){
        fprintf(out,"-1");
        return 0;
    }

    for(int i=0;i<=20000;++i) dmin[i]=minim;

    dmin[0]=0;
    for(int i=1;i<=n;++i){
        for(int j=W; j>=0; --j){
            if ( dmin[j] != minim )
                if ( dmin[j] + C[i] < dmin[ j + P[i] ] )
                    dmin[ j + P[i] ] = dmin[j] + C[i];
        }
    }

    for( int i = W; i <= 20000; ++i )
        minim = min( dmin[i], minim );

    fprintf(out,"%d",minim);
    return 0;
}