longestArray+1

#include<stdio.h>

void unesi(char niz[], int velicina) {
    char znak = getchar();
    if (znak == '\n') znak = getchar();
    int i = 0;
    while (i < velicina-1 && znak != '\n') {
        niz[i] = znak;
        i++;
        znak = getchar();
    }
    niz[i] = '\0';
}

int main(){
    char input[100],output[100];
    printf("Unesite ulaznu datoteku: ");
    unesi(input, sizeof input);
    FILE* open=fopen(input, "r");
    if(open==NULL){
        printf("Daoteka %s ne postoji",input);
        return 1;
    }
    printf("Unesite izlaznu datoteku: ");
    unesi(output, sizeof output);
    FILE* izlaz=fopen(output,"w");

    int c,pozMax,max=0;

    while((c=fgetc(open))!=EOF){
        int poz=ftell(open)-1;
        int slovo=c,brojac=1;
        for(c=fgetc(open);c!=EOF && c==slovo+1;c=fgetc(open),brojac++) slovo=c;

        if(brojac>max) max=brojac,pozMax=poz;

        if(c==EOF)break;
        fseek(open, -1, SEEK_CUR);
    }
    int i;
    fseek(open,pozMax,SEEK_SET);
    for(i=0,c=fgetc(open);i<max && c!=EOF;i++,c=fgetc(open))
        fputc(c,izlaz);
    fclose(open);
    fclose(izlaz);
    return 0;
}