#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
typedef long long ll;
using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
ll base = 1<<18;
ll inf = 1e18;
vector<pair<ll, ll>> T(2*base,{0,0});
vector<ll> lazy(2*base,0);
void push(ll v, ll l, ll r) {
if(!lazy[v] || v>=base) return;
for(auto x : {l,r}) {
T[x].first += lazy[v];
lazy[x] += lazy[v];
}
lazy[v] = 0;
}
void update(ll v, ll a, ll b, ll p, ll k, ll val) {
if(b < p || k < a) return;
if(p<=a&&b<=k) {
T[v].first += val;
lazy[v] += val;
return;
}
ll l=2*v; ll r=2*v+1; ll mid = (a+b)/2;
push(v,l,r);
update(l,a,mid,p,k,val);
update(r,mid+1,b,p,k,val);
T[v] = max(T[l], T[r]);
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
ll n,k,r;
cin >> n >> k >> r;
vector<ll> reqs(k);
vector<ll> a(n);
for(ll i=0; i<n; ++i) cin >> a[i];
while(r--) {
ll b, q;
cin >> b >> q;
reqs[b] = q;
}
vector<vector<ll>> pos(k);
vector<ll> idx(n+1), cnt(k, 1);
for(ll i=0; i<k; ++i) pos[i].push_back({0});
for(ll i=0; i<n; ++i) {
pos[a[i]].push_back(i+1);
idx[i+1] = cnt[a[i]]++;
}
for(ll i=0; i<base; ++i) {
T[i+base].second = i;
}
for(ll i=base-1; i>=1; --i) {
T[i] = max(T[i+i], T[i+i+1]);
}
for(ll i=0; i<k; ++i) if(reqs[i]==0) update(1,0,base-1,0,base-1,1);
ll best = -inf;
ll ans = inf;
for(ll i=1; i<=n; ++i) {
ll c = a[i-1];
if(reqs[c]==0) continue;
if(idx[i] >= reqs[c]) {
update(1,0,base-1,pos[c][idx[i]-reqs[c]],pos[c][idx[i]-reqs[c]+1]-1,1);
// cout << "[" << pos[c][idx[i]-reqs[c]] << ", " << pos[c][idx[i]-reqs[c]+1] << ") - " << c << "\n";
}
while(T[1].first==k) {
best = max(best,T[1].second);
update(1,0,base-1,T[1].second,T[1].second,-inf);
}
// cout << i << " " << best << "\n";
ans = min(ans, i-best);
}
if(ans==inf) cout << "impossible\n";
else cout << ans << "\n";
return 0;
}
