#include <stdlib.h>#include <string.h>
#include <stdio.h>
char * add(const char *, const char *);
char * substract(const char * as, const char * bs) {
int lena=strlen(as), lenb=strlen(bs), mlen=lena>lenb?lena:lenb;
char * tmp=(char *)malloc((mlen+3)*sizeof(char)), * x;
char a, b, c, atvitel=0;
int i;
if ((as[0]=='-')&&(bs[0]!='-')) { /* (-a) - b = -(a + b) */
x=add(as+1, bs);strcpy(tmp, "-");
strcat(tmp, x);return tmp;}
if ((as[0]!='-')&&(bs[0]=='-')) return add(as, bs+1); /* a - (-b) = a + b */
    if ((as[0]=='-')&&(bs[0]=='-')) { /* (-a) - (-b) = -(a - b)         x=substract(as+1, bs+1);
        strcpy(tmp, "-");
        strcat(tmp, x);
        return tmp;
    }
    for (i=0;i<mlen+1;i++) {
   if ((i==mlen)&&(atvitel==1)) {
            x=substract(bs, as);
            strcpy(tmp, "-"); strcat(tmp, x);
            return tmp;
        }
        /* Írásbeli kivonás elvégzése */
        if (i<lena) a=as[lena-i-1]-'0'; else a=0;
        if (i<lenb) b=bs[lenb-i-1]-'0'; else b=0;
        c=(a-b-atvitel)<0?(a-b-atvitel+10):a-b-atvitel;
        atvitel=(a-b-atvitel)<0?1:0;
        tmp[mlen-i]='0'+c;
    }
    /* Szöveg lezárása és kitakarítása */
    tmp[mlen+1]=0;
    i=tmp[0]=='-'?1:0;
    while ((tmp[i]=='0')&&(strlen(tmp)>1+i)) strcpy(&tmp[i], &tmp[i+1]);
    return tmp;
}
char * add(const char * as, const char * bs) {
    int lena=strlen(as), lenb=strlen(bs), mlen=lena>lenb?lena:lenb;
    char * tmp=(char *)malloc((mlen+3)*sizeof(char)), * x;
    char a, b, c, atvitel=0;
    int i; 
    memset(tmp, 0, mlen+3);
    if ((as[0]=='-')&&(bs[0]!='-')) return substract(bs, as+1); /* (-a) + b = b - a */
    if ((as[0]!='-')&&(bs[0]=='-')) return substract(as, bs+1); /* a + (-b) = a - b */
    if ((as[0]=='-')&&(bs[0]=='-')) { /* (-a) + (-b) = -(a + b) */
 x=add(as+1, bs+1);
strcpy(tmp, "-"); strcat(tmp, x); return tmp;
}for (i=0;i<mlen+1;i++) {
if (i<lena) a=as[lena-i-1]-'0'; else a=0;
if (i<lenb) b=bs[lenb-i-1]-'0'; else b=0;c=(a+b+atvitel)%10; atvitel=(a+b+atvitel)/10;tmp[mlen-i]='0'+c;
 }tmp[mlen+2]=0;
i=tmp[0]=='-'?1:0;
while ((tmp[i]=='0')&&(strlen(tmp)>1+i)) strcpy(&tmp[i], &tmp[i+1]);return tmp;}
int main() {
char a[101]="", b[101]="", * c, muvelet=' ';
FILE * fin, * fout; 
fin=fopen("be.txt", "r");
fscanf(fin, "%s\n", a);
fscanf(fin, "%c\n", &muvelet);
while (muvelet!='=') {
fscanf(fin, "%s\n", b);
if (muvelet=='+') c=add(a, b);
if (muvelet=='-') c=substract(a, b);
strcpy(a, c); free(c);
fscanf(fin, "%c\n", &muvelet);}fclose(fin);fout=fopen("ki.txt", "w");fprintf(fout, "%s\n", a);fclose(fout); return 0;}