#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
#define block_of_code if(true)
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
double rngesus_d(double l, double r){
double cur = rngesus(0, MASK(60) - 1);
cur /= MASK(60) - 1;
return l + cur * (r - l);
}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const int INF = 1e9 + 69;
struct SegmentTree{
int n;
vector<int> a;
SegmentTree(int _n){
n = _n;
a.resize(n * 2 + 2, 0);
}
void update(int i, int v){
i += n; a[i] += v;
while(i > 1){
i >>= 1;
a[i] = max(a[i * 2], a[i * 2 + 1]);
}
}
int get(int l, int r){
l += n; r += n + 1;
int ans = -INF;
while(l < r){
if (l & 1) maximize(ans, a[l++]);
if (r & 1) maximize(ans, a[--r]);
l >>= 1; r >>= 1;
}
return ans;
}
};
int main(void){
ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
clock_t start = clock();
int n, k, r; cin >> n >> k >> r;
vector<int> a(n);
for(int i = 0; i<n; ++i) cin >> a[i];
SegmentTree st(k);
for(int i = 0; i<r; ++i){
int j, x; cin >> j >> x;
st.update(j + 1, x);
}
int j = 0;
int ans = n + 1;
for(int i = 0; i<n; ++i){
st.update(a[i] + 1, -1);
while(j <= i && st.get(1, k) <= 0){
st.update(a[j] + 1, 1);
j++;
}
if (j > 0) minimize(ans, i - j + 2);
}
if (ans > n){
cout << "impossible\n";
return 0;
}
cout << ans << "\n";
cerr << "Time elapsed: " << clock() - start << " ms\n";
return 0;
}
