1 2 3 4 5 6 7 8 9 10 11
#include<stdio.h> int main(){ int i,j,k=1; printf("%d",k); for(i=0,j=3;i<19;++i,j+=2){ if(i%2){k+=j;printf("+%d",j);} else{k-=j;printf("-%d",j);} } printf("=%d",k); return 0; }
1
1-3+5-7+9-11+13-15+17-19+21-23+25-27+29-31+33-35+37-39=-20