#include <bits/stdc++.h>

using namespace std;
const int MaxN = 1005;
int d[MaxN][20003], n;
struct miau{int a, b;} v[MaxN];

int main() {
    cin >> n;
    cin >> v[0].b;
    for (int i = 1; i < n; ++i) {
        cin >> v[i].a >> v[i].b;
    }
    for (int i = 0; i <= n; ++i) {
        for (int j = 0; j <= 20000; ++j) d[i][j] = -1e9;
    }
    for (int i = 0; i < v[0].b; ++i) d[1][i] = i;

    int ans = 0;
    for (int i = 2; i <= n; ++i) {
        int maxi = -1e9;

        for (int k = v[i - 1].a; k < v[i - 1].a + v[i - 1].b; ++k)
            d[i][k - v[i - 1].a] = max(d[i][k - v[i - 1].a], d[i - 1][k]);

        for (int k = v[i - 1].a + v[i - 1].b; k <= 20000; ++k)
            d[i][k] = max(d[i][k], d[i - 1][k]);

        for (int k = 0; k < v[i - 1].a; ++k)
            maxi = max(maxi, d[i - 1][k]);

        for (int j = 0; j < v[i - 1].b; ++j)
             d[i][j] = j + max(d[i][j] - j, maxi);

        for (int j = v[i - 1].b; j < v[i - 1].b + v[i - 1].a; ++j)
            d[i][j] = max(d[i][j], d[i - 1][j - v[i - 1].b] + v[i - 1].b);

    }
    for (int i = 0; i <= 20000; ++i) ans = max(ans, d[n][i]);
    cout << ans << '\n';
    return 0;
}