#include<stdio.h>
#include<algorithm>
#include<cstring>
#include<tuple>
typedef long long ll;
constexpr int pw10[8]{1,10,100,1000,10000,100000,1000000,10000000};
inline std::tuple<int,int> read() {
    static char str[9]{};
    scanf("%s",str);
    int len{int(std::strlen(str))-2};
    int x,y;
    sscanf(str,"%d.%d",&x,&y);
    return {len,x*pw10[len]+y};
}
int p[105];
int main() {
    int n,l{0};
    scanf("%d",&n);
    for(int i=1;i<=n;i++) {
        std::tie(l,p[i])=read();
    }
    ++l;
    for(int i=1;i<=n;i++) {
        p[i]*=10;
    }
    for(int k=1;k<=pw10[l-1];k++) {
        ll min{0},max{0};
        for(int i=1;i<=n;i++) {
            ll lt{std::max<ll>(0,(ll(p[i]-5)*k+pw10[l]-1)/pw10[l])};
            ll rt{(ll(p[i]+5)*k-1)/pw10[l]};
            min+=lt,max+=rt;
        }
        if(min<=k&&k<=max) {
            printf("%d\n",k);
            return 0;
        }
    }
    puts("-1");
    return 0;
}