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#include<stdio.h>
#include<ctype.h>

#define  SIZE  10

int atoi(char s[]);

int main(int argc, char *argv[])
{
  int counter=0;
  char s[SIZE];
  if (argc!=2) printf("Usage: progname integer\n");
  while(*argv[1])  s[counter++]=(*argv[1]++);
  printf("Twice Result=%d\n",2*atoi(s));
return 0;
}
int atoi(char s[])
{
  int n, i,sign;

 for(i=0; isspace(s[i]); i++);

sign=(s[i]=='-')? -1: 1;
if(s[i] == '+' || s[i] == '-') i++;
 for(n=0; isdigit(s[i]); i++)
   n=10*n + (s[i]-'0');

return sign*n;
}

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