#include <bits/stdc++.h>   using namespace std;   template <class T>   T sqr(T a) {     return (a) * (a);   }   template <class T>   T abs(T a) {     return (a < 0) ? -(a) : (a);   }   const double Pi = acos(-1.0);   const double eps = 1e-10;   const int INF = 1000 * 1000 * 1000;   const double phi = 0.5 + sqrt(1.25);   int main() {     string Less =  z , More =    , tmp =   ;     int n;     scanf( %d n , &n);     for (int i = 0, _n = (n)-1; i <= _n; ++i) {       getline(cin, tmp);       Less = min(Less, tmp);       More = max(More, tmp);     }     int i = 0, m = ((int)((Less).size()));     bool coincide = 1;     while (i < m && coincide)       if (Less.substr(0, i + 1) == More.substr(0, i + 1))         i++;       else         coincide = 0;     printf( %d n , i);     return 0;   }   