Simple file input/output question

#include <stdio.h>
#include <string.h>
#define CMAX 10000000
#define PMAX 3000
int stack=0;
char space=' ';
char str[CMAX], pat[PMAX];
int stack_2[PMAX];
int nfind(char*, char*);
int main(){
    FILE *fp=fopen("string.txt", "rt");
    FILE *fp2=fopen("pattern.txt", "rt");
    fgets(str, CMAX, fp);
    fgets(pat, PMAX, fp2);
    for(int i=0;i<PMAX;i++)
        stack_2[i]=-1;
    nfind(str, pat);
    int S;
    S=stack;
    FILE *fp3;
    fp3=fopen("result.txt", "wt");
    if(fp3==NULL)
    {
        printf("failed\n");
        return 1;
    }
    fprintf(fp3, "%d\n", stack);
    while(stack>0)
    {
        fprintf(fp3, "%d ", stack_2[stack-1]);
        fprintf(fp3, "%c", space);
        stack--;
    }
    fclose(fp);
    fclose(fp2);
    fclose(fp3);
    return 0;
}
int m=0;
int nfind(char *string, char *pat)
{
    int i, j, start=0;
    int n;
    int lasts=strlen(string)-1;
    int lastp=strlen(pat)-1;
    int endmatch=lastp;
    for(i=0;endmatch<=lasts;endmatch++, start++){
        if(string[endmatch]==pat[lastp])
        {
            for(j=0, i=start;j<=lastp&&string[i]==pat[j];i++)
            {
                j++;

            }


        }
        if(j==lastp+1)
       {

             stack_2[m]=start;
             m++;
             stack++;
             j=0;
        }
        else
            continue;

    }
    return 0;

}