tinh toan

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int cal(char s[])
{
    char str [1000];
    int a, sum = 0;
    int i=0, l= strlen(s);
    while (i < l)
    {
        if (s[i] == '+') i++;
        sscanf(s + i, "%d", &a);    // lay tung so trong chuoi
        sum += a;
        sprintf(str, "%d", a);      // doi so a ra chuoi str de xac dinh vi tri i
        i += strlen(str);
    }
    return sum;
}

int main()
{
    char s[1000], ch;
    int result;
    FILE *f = NULL;
    f=fopen("input.inp","rt");
    if (f==NULL)
    {
        printf("Error opening file");
        return 0;
    }
    while((fscanf(f,"%s%c",&s,&ch)!=EOF))
    {
        result = cal(s);
        printf("%s = %d\n", s, result);
    }
    return 0;
}