/* Function atoi(s) to convert a string to integer. */

#include <stdio.h>

int atoi(char str[]);

main()
{
	printf("%d\n",atoi("123"));
}

int atoi(char str[])
{
	int i, num=0;
	for(i=0;str[i]!='\0';i++)
		num=num*10+str[i]-'0';
	return num;
}