#include<bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1000000007;
int n,k,A;
int s[15],v[15];
int dp[2005];
int val[2005];
signed main(){
	cin >> n >> k >> A;
	for(int i = 1;i<=n;i++)val[i] = A;
	for(int i = 1;i<=k;i++){
		int s,v;cin >>s  >> v;
		val[s] = v;
	}
	dp[1] =1;
	for(int i = 2;i<=n;i++){
		for(int j = 1;j<i;j++){
			dp[i] = (dp[j]*dp[i-j]*val[j]+dp[i])%mod;
		}
	}
	cout << dp[n] << endl;
	return 0;
}/*
6 2 1
2 3
4 5
*/