Implement substring in C

#include<stdlib.h>char a[6] = {'a','b','c','d','e','f'};char b[3] = {'c','d','e'};int subString(char* a, int aLen, char* b, int bLen){int i = 0;int j = 0;for(; i < aLen - bLen; i++){for(; j < bLen; j++){if(a[i+j] != b[j]){break;}if(j == bLen - 1){return i;} }}return -1;}int main(){int result = subString(a,6,b,3);printf("%d",result);}