#include <iostream>

using namespace std;

int n;
int cena[2005], tezina[2005];
int W;

int rec(int at, int W_left) {
    if(at == n) {
        return 0;
    }
    
    int result = -2e9;
    // da ne go zememe elementot
    result = max(result, rec(at + 1, W_left));
    
    if(W_left - tezina[at] >= 0)
        result = max(result, rec(at + 1, W_left - tezina[at]) + cena[at]);
    return result;
}
int main() {
    cin >> n;
    for(int i = 0; i < n; i++) {
        cin >> cena[i] >> tezina[i];
    }
    cin >> W;
    cout << rec(0, W) << endl;
    return 0;
}