#include <bits/stdc++.h>
using namespace std;
#define SZ(x) int(x.size())
const int MXN = 2e5+5;
int n, k, r, a[MXN], b[MXN];
vector<int> vec[MXN];
int32_t main() {
cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
cin >> n >> k >> r;
for(int i=0; i<n; i++) cin >> a[i], vec[a[i]].push_back(i);
int mx = 0;
while(r--) {
int x, y;
cin >> x >> y;
if(y>SZ(vec[x])) {
cout << "impossible\n";
return 0;
}
mx = max(mx, vec[x][y-1]);
b[x] = y;
}
int ans = n;
set<int> st;
for(int i=0; i<n; i++) {
if(b[a[i]]) {
int pos = lower_bound(vec[a[i]].begin(), vec[a[i]].end(), i)-vec[a[i]].begin();
if(pos-b[a[i]]>=0) st.erase(vec[a[i]][pos-b[a[i]]]);
if(pos-b[a[i]]+1>=0) st.insert(vec[a[i]][pos-b[a[i]]+1]);
}
if(i>=mx) ans = min(ans, i - (*st.begin()) + 1);
}
cout << ans << '\n';
return 0;
}
