7-12

#include<stdio.h>
int main(void)
{
    int i,number;
    char str[10];

    printf("Enter a string:");
    i=0;
    while((str[i]=getchar())!='\n')
        i++;
    str[i]='\0';

    number=0;
    for(i=0;str[i]!='\0';i++)
        if(str[i]>='0'&&  str[i]<='9')
            number=number*10+str[i]-'0';

    printf("digit=%d\n",number);

    return 0;
}