#include<bits/stdc++.h>
using namespace std;
#define FOR(i,s,t) for(int i=(s),_t=(t); i<=_t; ++i)
#define DOR(i,s,t) for(int i=(s),_t=(t); i>=_t; --i)
typedef long long ll;
typedef double db;
const db eps=1e-8;
int sgn(db x) {
    return x<-eps?-1:x>eps;
}
const int M=1115;
const int N=222;
db a[M][N];
int pos[N];
db b[N];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(9);
    int n,c,qr;
    cin >> n >> c >> qr;
    int m=0;
    FOR(i,1,n-1) {
        db v;
        cin >> v;
        if(v<-0.5) continue;
        ++m;
        a[m][c*2+i]=1;
        a[m][c*2+n]=log(v);
    }
    FOR(i,1,n) {
        FOR(j,1,c) {
            db v;
            cin >> v;
            if(v<-0.5) continue;
            ++m;
            a[m][j]=1;
            a[m][c+j]=i-1;
            FOR(k,1,i-1) {
                a[m][c*2+k]=1;
            }
            a[m][c*2+n]=log(v);
        }
    }
    int l=c*2+n;
    int K=0;
    FOR(i,1,m) {
        int &p=pos[i];
        p=pos[i-1]+1;
        int q;
        while(p<l) {
            q=0;
            FOR(j,i,m) if(sgn(a[j][p])) if(!q || a[j][p]>a[q][p]) q=j;
            if(q) break;
            p++;
        }
        if(p==l) break;
        FOR(j,p,l) swap(a[i][j],a[q][j]);
        FOR(j,i+1,m) DOR(k,l,p) a[j][k]-=a[i][k]*a[j][p]/a[i][p];
        K=i;
    }
    while(qr--) {
        int x,y;
        cin >> x >> y;
        FOR(i,1,l) b[i]=0;

        b[x]=1;
        b[c+x]=y-1;
        FOR(k,1,y-1) b[c*2+k]=1;

        FOR(i,1,K) DOR(j,l,pos[i]) b[j]-=a[i][j]*b[pos[i]]/a[i][pos[i]];
        int w=1;
        FOR(i,1,l-1) if(sgn(b[i])) {w=0;break;}
        db res=exp(-b[l]);
        if(w==0) res=-1;
        cout << res << '\n';
    }
    return 0;
}