#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define fi first
#define se second
#define vi vector<int>
#define vll vector<long long>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng64(chrono::steady_clock::now().time_since_epoch().count());
inline int rand(int l,int r){return uniform_int_distribution<int>(l, r)(rng);}
inline ll rand(ll l,ll r){return uniform_int_distribution<ll>(l, r)(rng64);}
#ifdef DEBUG
auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X)
#else
#define debug(...){}
#endif
struct custom_hash {
static uint64_t splitmix64(uint64_t x) {
x += 0x9e3779b97f4a7c15;
x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
return x ^ (x >> 31);
}
size_t operator()(uint64_t x) const {
static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
return splitmix64(x + FIXED_RANDOM);
}
};
const int MAXN = 2e5 + 7;
vi pos[MAXN];
int mn[MAXN];
int a[MAXN];
int c[MAXN];
int wsk[MAXN];
int n, k, r;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> k >> r;
for(int i = 1; i <= n; i++){
cin >> a[i];
pos[a[i]].pb(i);
}
for(int i = 1; i <= r; i++){
int x;
cin >> x;
cin >> mn[x];
}
int mx = 1;
for(int i = 0; i < k; i++){
if(sz(pos[i]) < mn[i]){
cout << "impossible\n";
return 0;
}
if(mn[i] == 0){
continue;
}
wsk[i] = mn[i];
c[i] = sz(pos[i]);
mx = max(mx, pos[i][mn[i] - 1]);
}
int ans = n;
for(int i = 1; i <= n; i++){
ans = min(ans, mx - i + 1);
if(mn[a[i]] > 0){
if(wsk[a[i]] >= sz(pos[a[i]])){
break;
}
mx = max(mx, pos[a[i]][wsk[a[i]]]);
wsk[a[i]]++;
}
}
cout << ans << '\n';
return 0;
}
