#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define vl vector<ll>
#define vi vector<int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define all(v) v.begin(), v.end()
#define pb push_back
#define f first
#define s second
using namespace std;
using namespace __gnu_pbds;
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
const ll sz = 2e5+5;
vl g[sz];
ll grid[15][sz];
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll tests = 1;
//cin >> tests;
while(tests--)
{
ll n, k, r, i, j, ans = LLONG_MAX;
cin >> n >> k >> r;
vl v(n+5);
map<ll, ll>mp;
for(i = 1; i <= n; i++)
cin >> v[i];
vl vect;
for(i = 1; i <= r; i++)
{
ll x, y;
cin >> x >> y;
mp[x] = y;
vect.pb(x);
}
for(i = 1; i <= n; i++)
{
map<ll, ll>mp2;
for(j = i; j <= n; j++)
{
mp2[v[j]]++;
bool possible = true;
for(auto u : vect)
{
if(mp2[u] < mp[u])
{
possible = false;
break;
}
}
if(possible)
ans = min(ans, j - i + 1);
}
}
if(ans == LLONG_MAX)
cout << "impossible\n";
else
cout << ans << "\n";
}
}
