#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <math.h>
#include <ctype.h>
#include <time.h>

typedef long long ll;
typedef unsigned long long ull;

ll max(ll a, ll b) {
    return (a > b) ? a : b;
}

ll toll(char c) {
    if(isdigit(c))
        return c - '0';
    return c - 'a' + 10;
}

ll upper;

long double power;

ull todec(char * str, ll x) {
    ull res = 0;
    ull mul = 1;

    char * end = str;
    while(*end)
        ++end;
    --end;

    mul = 1;
    while(end >= str) {
        if((power - res) / mul < toll(*end)) {
            upper = 1;
            break;
        }
        res += toll(*end) * mul;
        mul *= x;
        --end;
    }

    return res;
}

void parse(char * str, char * a, char * b, char * c, char * d) {
    while(*str != '+' && *str != '*')
        *a++ = *str++;
    *a = 0;
    *d = *str;
    ++str;
    while(*str != '=')
        *b++ = *str++;
    *b = 0;
    ++str;
    while(*str)
        *c++ = *str++;
    *c = 0;
}

int main()
{
    power = pow(2, 64);

    char a[1001][100], b[1001][100], c[1001][100], d[1001];
    ll n;
    scanf("%lld", &n);

    long long min_base = -1;
    for(ll i = 0; i < n; i++) {
        char arr[1000];
        scanf("%s", arr);
        parse(arr, a[i], b[i], c[i], &d[i]);
        for(ll j = 0; a[i][j]; ++j)
            min_base = max(min_base, toll(a[i][j]));
        for(ll j = 0; b[i][j]; ++j)
            min_base = max(min_base, toll(b[i][j]));
        for(ll j = 0; c[i][j]; ++j)
            min_base = max(min_base, toll(c[i][j]));
    }

    clock_t time = clock();

    ll first = -1, second = -1;
    upper = 0;
    for(ll i = min_base + 1; i < min_base + 1500 && (clock() - time) / CLOCKS_PER_SEC < 4.0; i++) {
        ll ex = 0;
        for(ll j = 0; j < n; j++) {
            if(d[j] == '+') {
                if(todec(a[j], i) + todec(b[j], i) != todec(c[j], i)) {
                    ex = 1;
                    break;
                }
            } else {
                if(todec(a[j], i) * todec(b[j], i) != todec(c[j], i)) {
                    ex = 1;
                    break;
                }
            }
        }
        if(upper)
            break;

        if(!ex) {
            if(first == -1)
                first = i;
            else {
                second = i;
                printf("-1");
                return 0;
            }
        }
        upper = 0;
    }
    if(first == -1)
        printf("0");
    else
        printf("%lld", first);

    return 0;
}