#include <stdio.h>
void main(void){
	char s[1000000] = "a";
	scanf("%s",s);
	char t[1000000] = "a";
	scanf("%s",t);
	int n = 0;
	scanf("%d",&n);
	printf("%s",s);
	for(int i = 0 ; i < n ; i++){
		printf("_%s",t);
	}
}