function Main(input){
  input = input.split("\n");
  var a = input[1].split("");
  var b = input[2].split("");
  var c = input[3].split("");
  var sum = a.length*2;
  for(var i=0;i<a.length;i++){
    var x = 0;
    if(a[i]==b[i]) x++;
    if(c[i]==b[i]) x++;
    if(a[i]==c[i]) x++;
    if(x == 3) sum -= 2;
    else if(x == 1) sum--;
  }
  console.log(sum);
  }Main(require("fs").readFileSync("/dev/stdin", "utf8").trim());