#include<cstdio>
#include<cstdint>
#include<climits>
#include<algorithm>
using namespace std;

int main()
{
	int n, t, v;
	int sumW = 0, sumL = 0;
	int ans = INT_MAX;
	int w[100], l[100];
	int dp[10001] = {0};
	
	scanf("%d%d%d", &n, &t, &v);
	
	for (int i = 0; i < n; ++i)
	{
		scanf("%d%d", &w[i], &l[i]);
		sumW += w[i];
		sumL += l[i];
	}
	
	for (int i = 0; i < n; ++i)
	{
		for (int j = sumW; j >= w[i]; --j)
		{
			dp[j] = max(dp[j], dp[j - w[i]] + l[i]);
		}
	}
	
	for (int j = t; j <= sumW; ++j)
	{
		ans = min(ans, (j - t) * v + (sumL - dp[j]));
	}
	
	if (t >= sumW)
	{
		ans = 0;
	}
	
	printf("%d\n", ans);
	return 0;
}