    	function Main(input){
    		var input = input.split(/\r\n|\r|\n/);
        	var n = parseInt(input[0],10);
        	var a = input[1].split("");
        	var b = input[2].split("");
        	var c = input[3].split("");
        	var cnt = 0;
        	var p = 0;
        	while (cnt < n) {
        		p = 0;
        		if (a[cnt] == b[cnt]){
        			p++;
        		}
        		if (a[cnt] == c[cnt]){
        			p++;
        		}
        		if (b[cnt] == c[cnt]){
        			p++;
        		}
        		cnt++; 
    		}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));