#include<bits/stdc++.h>
#define LINT long long int
#define ULINT unsigned long long int
#define INF 99999999999

using namespace std;



int main(){
    ifstream fin("input.txt");
    string s;
    getline(fin, s);
    int lc = 0, rc = 0, c = 0, index = 0, lli, li = -1, ri = -1, rri;
    bool f = true;
    for (int i = 0; i < s.size(); ++i) {
        if (s[i] == '}') {
            lc++;
            lli = index;
        } else
            if (s[i] == '{') {
                break;
            }
        index++;
    }
    for (int i = index; i < s.size(); ++i) {
        if (s[i] == '}') {
            c--;
            f = true;
            rc = 0;
            if (ri == -1) {
                ri = index;
            }
        } else
            if (s[i] == '{') {
                rc++;
                if (f && c == 0) {
                    li = index;
                }
                c++;
                f = false;
            }
        index++;
    }
    c -= rc;
    if (lc + rc > 1 || (c > 0 && lc + rc > 0) || (c == 0 && lc + rc == 0) || abs(c) > 1) {
        cout << -1;
        return 0;
    }
    if (c == 1) {
        cout << li + 1;
    } else
        cout << ri + 1;
}